Imported recent work in master, minor conflict fixed in paper.mk

Only two conflicts came up in the newly added comments of 'paper.mk' in the
Maneage branch. It happened because in this project we don't use
'pdflatex', but 'latex' alone.

6 files changed, 2015 insertions, 2124 deletions

diff --git a/reproduce/software/make/atlas-multiple.mk b/reproduce/software/make/atlas-multiple.mk
index 9bd26b1..9bd26b1 100755..100644
--- a/reproduce/software/make/atlas-multiple.mk
+++ b/reproduce/software/make/atlas-multiple.mk
diff --git a/reproduce/software/make/atlas-single.mk b/reproduce/software/make/atlas-single.mk
index 29373e0..29373e0 100755..100644
--- a/reproduce/software/make/atlas-single.mk
+++ b/reproduce/software/make/atlas-single.mk
diff --git a/reproduce/software/make/basic.mk b/reproduce/software/make/basic.mk
index 82bc42d..94bb5d4 100644
--- a/reproduce/software/make/basic.mk
+++ b/reproduce/software/make/basic.mk
@@ -5,13 +5,19 @@
 #                      !!!!! IMPORTANT NOTES !!!!!
 #
 # This Makefile will be run by the initial `./project configure' script. It
-# is not included into the project after that.
+# is not included into the project afterwards.
 #
-# This Makefile builds very low-level and basic tools like GNU Tar, GNU
-# Bash, GNU Make, GCC and etc. Therefore this is the only Makefile in the
-# project where you CANNOT assume that GNU Bash or GNU Make are used. After
-# this Makefile (where GNU Bash and GNU Make are built), other Makefiles
-# can safely assume the fixed version of all these software.
+# This Makefile builds low-level and basic tools that are necessary in any
+# project like like GNU Tar, GNU Bash, GNU Make, GCC and etc. But before
+# control reaches here, the 'configure.sh' script has already built the
+# extremely low-level tools: Lzip (a compressing program), GNU Make (to be
+# able to run this Makefile with a fixed version), Dash (a minimalist
+# POSIX-compatible shell) and Flock (to allow locking files, and
+# serializing when necessary: downloading during the software building
+# phase). Thanks to GNU Make and Dash, we can assume a fixed structure in
+# this Makefile. However, the 'PATH's in this Makefile still include the
+# host's paths because we will be using the hosts tools (gradually
+# decreasing) to build our own tools.
 #
 # ------------------------------------------------------------------------
 #
@@ -31,13 +37,17 @@
 # You should have received a copy of the GNU General Public License
 # along with this Makefile.  If not, see <http://www.gnu.org/licenses/>.
 
-
 # Top level environment
 include reproduce/software/config/LOCAL.conf
 include reproduce/software/make/build-rules.mk
 include reproduce/software/config/versions.conf
 include reproduce/software/config/checksums.conf
 
+# The optional URLs of software. Note that these may need the software
+# version, so it is important that they be loaded after 'versions.conf'.
+include reproduce/software/config/urls.conf
+
+# Basic directories
 lockdir = $(BDIR)/locks
 tdir    = $(BDIR)/software/tarballs
 ddir    = $(BDIR)/software/build-tmp
@@ -46,31 +56,34 @@ ibdir   = $(BDIR)/software/installed/bin
 ildir   = $(BDIR)/software/installed/lib
 ibidir  = $(BDIR)/software/installed/version-info/proglib
 
-# We'll need the system's PATH for making links to low-level programs we
-# won't be building ourselves.
-syspath := $(PATH)
+# Ultimate Makefile target.
+targets-proglib = low-level-links gcc-$(gcc-version)
+all: $(foreach p, $(targets-proglib), $(ibidir)/$(p))
 
+# Define the shell environment
+# ----------------------------
+#
+# We build GNU Bash here in 'basic.mk'. So here we must must assume DASH
+# shell that was built before calling this Makefile:
+# http://gondor.apana.org.au/~herbert/dash. DASH is a minimalist POSIX
+# shell, so it doesn't have startup options like '--noprofile --norc'. But
+# from its manual, to load startup files, Dash actually requires that it be
+# called with a '-' before it (for example '-dash'), so it shouldn't be
+# loading any startup files if it was interpretted properly.
+#
 # As we build more programs, we want to use this project's built programs
-# and libraries, not the host's.
+# and libraries, not the host's, so in all PATH-related environments, our
+# own build-directory comes first.
 .ONESHELL:
+.SHELLFLAGS := -e -c
 export CCACHE_DISABLE := 1
+export SHELL := $(ibdir)/dash
 export PATH := $(ibdir):$(PATH)
 export PKG_CONFIG_PATH := $(ildir)/pkgconfig
 export PKG_CONFIG_LIBDIR := $(ildir)/pkgconfig
 export CPPFLAGS := -I$(idir)/include $(CPPFLAGS)
 export LDFLAGS := $(rpath_command) -L$(ildir) $(LDFLAGS)
 
-# Note that we build GNU Bash here in 'basic.mk'. So we can't assume Bash
-# in this Makefile and use the DASH shell that was before calling this
-# Makefile: http://gondor.apana.org.au/~herbert/dash. Dash is a minimalist
-# POSIX shell, so it doesn't have startup options like '--noprofile
-# --norc'. But from its manual, to load startup files, Dash actually
-# requires that it be called with a '-' before it (for example '-dash'), so
-# it shouldn't be loading any startup files if it was interpretted
-# properly.
-.SHELLFLAGS := -e -c
-export SHELL := $(ibdir)/dash
-
 # This is the "basic" tools where we are relying on the host operating
 # system, but are slowly populating our basic software envirnoment. To run
 # (system or template) programs, `LD_LIBRARY_PATH' is necessary, so here,
@@ -86,202 +99,29 @@ export LD_LIBRARY_PATH := $(shell echo $(LD_LIBRARY_PATH):$(ildir) \
 # causes crashs (see bug #56682). So we'll just give it no value at all.
 export DYLD_LIBRARY_PATH :=
 
-# Recipe startup script.
-export PROJECT_STATUS := configure_basic
-export BASH_ENV := $(shell pwd)/reproduce/software/shell/bashrc.sh
-
-# Define the top-level basic programs (that don't depend on any other).
-top-level-programs = low-level-links gcc
-all: $(foreach p, $(top-level-programs), $(ibidir)/$(p))
-
-# Servers to use as backup, later this should go in a file that is not
-# under version control (the actual server that the tarbal comes from is
-# irrelevant).
-backupservers := $(shell awk '!/^#/{printf "%s ", $$1}' \
-                         reproduce/software/config/servers-backup.conf)
-
-
-
-
-
-
-# Tarballs
-# --------
-#
-# Prepare tarballs. Difference with that in `high-level.mk': `.ONESHELL' is
-# not recognized by some versions of Make (even older GNU Makes). So we'll
-# have to make sure the recipe doesn't break into multiple shell calls (so
-# we can preserve the variables).
-#
-# Software with main webpage at our backup repository
-# (http://akhlaghi.org/maneage-software): As of our latest check their
-# major release tarballs either crash or don't build on some systems (for
-# example Make or Gzip), or they don't exist (for example Bzip2). So we are
-# building them from their Git history (which builds properly) or host them
-# directly.
+# Servers to use as backup. Maneage already has some fixed servers that can
+# be used to download software tarballs. They are in a configuation
+# file. But we give precedence to the "user" backup servers.
 #
-# In the first case, we used their Git repo and bootstrapped them (just
-# like Gnuastro) and built the most recent tarball off of that. In the case
-# of Bzip2: its webpage has expired and doesn't host the data any more. It
-# is available on the link below (archive.org):
+# One important "user" server (which the user doesn't actually give, but is
+# found at configuration time in 'configure.sh') is Zenodo (see the
+# description in 'configure.sh' for more on why this depends on
+# configuration time).
 #
-# https://web.archive.org/web/20180624184806/http://www.bzip.org/1.0.6/bzip2-1.0.6.tar.gz
-#
-# However, downloading from this link is slow (because its just a link). So
-# its easier to just keep a with the others.
-$(lockdir): | $(BDIR); mkdir $@
+# Afer putting everything together, we use the first server as the
+# reference for all software if their '-url' variable isn't defined (in
+# 'reproduce/software/config/urls.conf').
 downloadwrapper = ./reproduce/analysis/bash/download-multi-try
-tarballs = $(foreach t, bash-$(bash-version).tar.lz \
-                        binutils-$(binutils-version).tar.lz \
-                        bzip2-$(bzip2-version).tar.gz \
-                        cert.pem \
-                        coreutils-$(coreutils-version).tar.xz \
-                        curl-$(curl-version).tar.gz \
-                        diffutils-$(diffutils-version).tar.xz \
-                        file-$(file-version).tar.gz \
-                        findutils-$(findutils-version).tar.xz \
-                        gawk-$(gawk-version).tar.lz \
-                        gcc-$(gcc-version).tar.xz \
-                        gettext-$(gettext-version).tar.xz \
-                        git-$(git-version).tar.xz \
-                        gmp-$(gmp-version).tar.lz \
-                        grep-$(grep-version).tar.xz \
-                        gzip-$(gzip-version).tar.lz \
-                        isl-$(isl-version).tar.bz2 \
-                        libbsd-$(libbsd-version).tar.xz	\
-                        libiconv-$(libiconv-version).tar.gz \
-                        libtool-$(libtool-version).tar.xz \
-                        libunistring-$(libunistring-version).tar.xz \
-                        libxml2-$(libxml2-version).tar.gz \
-                        m4-$(m4-version).tar.gz \
-                        metastore-$(metastore-version).tar.gz \
-                        mpfr-$(mpfr-version).tar.xz \
-                        mpc-$(mpc-version).tar.gz \
-                        ncurses-$(ncurses-version).tar.gz \
-                        openssl-$(openssl-version).tar.gz \
-                        patchelf-$(patchelf-version).tar.gz \
-                        perl-$(perl-version).tar.gz \
-                        pkg-config-$(pkgconfig-version).tar.gz \
-                        readline-$(readline-version).tar.gz \
-                        sed-$(sed-version).tar.xz \
-                        tar-$(tar-version).tar.gz \
-                        texinfo-$(texinfo-version).tar.xz \
-                        unzip-$(unzip-version).tar.gz \
-                        wget-$(wget-version).tar.lz \
-                        which-$(which-version).tar.gz \
-                        xz-$(xz-version).tar.gz \
-                        zip-$(zip-version).tar.gz \
-                        zlib-$(zlib-version).tar.gz \
-                      , $(tdir)/$(t) )
-$(tarballs): $(tdir)/%: | $(lockdir)
-
-        # Remove the version numbers and suffix from the tarball name so we
-        # can search more easily only with the program name. This requires
-        # the first character of the version to be a digit: packages such
-        # as `foo' and `foo-3' will not be distinguished, but `foo' and
-        # `foo2' will be distinguished.
-	@n=$$(echo $* | sed -e's/-[0-9]/ /' -e's/\./ /g' \
-	             | awk '{print $$1}' )
-
-	mergenames=1; \
-	if   [ $$n = bash      ]; then c=$(bash-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = binutils  ]; then c=$(binutils-checksum); w=http://ftp.gnu.org/gnu/binutils
-	elif [ $$n = bzip2     ]; then c=$(bzip2-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = cert      ]; then c=$(cert-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = coreutils ]; then c=$(coreutils-checksum); w=http://ftp.gnu.org/gnu/coreutils
-	elif [ $$n = curl      ]; then c=$(curl-checksum); w=https://curl.haxx.se/download
-	elif [ $$n = diffutils ]; then c=$(diffutils-checksum); w=http://ftp.gnu.org/gnu/diffutils
-	elif [ $$n = file      ]; then c=$(file-checksum); w=ftp://ftp.astron.com/pub/file
-	elif [ $$n = findutils ]; then c=$(findutils-checksum); w=http://ftp.gnu.org/gnu/findutils
-	elif [ $$n = gawk      ]; then c=$(gawk-checksum); w=http://ftp.gnu.org/gnu/gawk
-	elif [ $$n = gcc       ]; then c=$(gcc-checksum); w=http://ftp.gnu.org/gnu/gcc/gcc-$(gcc-version)
-	elif [ $$n = gettext   ]; then c=$(gettext-checksum); w=https://ftp.gnu.org/gnu/gettext
-	elif [ $$n = git       ]; then c=$(git-checksum); w=http://mirrors.edge.kernel.org/pub/software/scm/git
-	elif [ $$n = gmp       ]; then c=$(gmp-checksum); w=https://gmplib.org/download/gmp
-	elif [ $$n = grep      ]; then c=$(grep-checksum); w=http://ftp.gnu.org/gnu/grep
-	elif [ $$n = gzip      ]; then c=$(gzip-checksum); w=http://akhlaghi.org/src
-	elif [ $$n = isl       ]; then c=$(isl-checksum); w=ftp://gcc.gnu.org/pub/gcc/infrastructure
-	elif [ $$n = libbsd    ]; then c=$(libbsd-checksum); w=http://libbsd.freedesktop.org/releases
-	elif [ $$n = libiconv  ]; then c=$(libiconv-checksum); w=https://ftp.gnu.org/pub/gnu/libiconv
-	elif [ $$n = libtool   ]; then c=$(libtool-checksum); w=http://ftp.gnu.org/gnu/libtool
-	elif [ $$n = libunistring ]; then c=$(libunistring-checksum); w=http://ftp.gnu.org/gnu/libunistring
-	elif [ $$n = libxml2   ]; then c=$(libxml2-checksum); w=ftp://xmlsoft.org/libxml2
-	elif [ $$n = m4        ]; then
-	  mergenames=0
-	  c=$(m4-checksum)
-	  w=http://akhlaghi.org/maneage-software/m4-1.4.18-patched.tar.gz
-	elif [ $$n = metastore ]; then c=$(metastore-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = mpc       ]; then c=$(mpc-checksum); w=http://ftp.gnu.org/gnu/mpc
-	elif [ $$n = mpfr      ]; then c=$(mpfr-checksum); w=http://www.mpfr.org/mpfr-current
-	elif [ $$n = ncurses   ]; then c=$(ncurses-checksum); w=http://ftp.gnu.org/gnu/ncurses
-	elif [ $$n = openssl   ]; then c=$(openssl-checksum); w=http://www.openssl.org/source
-	elif [ $$n = patchelf  ]; then c=$(patchelf-checksum); w=http://nixos.org/releases/patchelf/patchelf-$(patchelf-version)
-	elif [ $$n = perl      ]; then
-	  c=$(perl-checksum)
-	  v=$$(echo $(perl-version) | sed -e's/\./ /g' | awk '{printf("%d.0", $$1)}')
-	  w=https://www.cpan.org/src/$$v
-	elif [ $$n = pkg-config ]; then c=$(pkgconfig-checksum); w=http://pkg-config.freedesktop.org/releases
-	elif [ $$n = readline  ]; then c=$(readline-checksum); w=http://ftp.gnu.org/gnu/readline
-	elif [ $$n = sed       ]; then c=$(sed-checksum); w=http://ftp.gnu.org/gnu/sed
-	elif [ $$n = tar       ]; then c=$(tar-checksum); w=http://ftp.gnu.org/gnu/tar
-	elif [ $$n = texinfo   ]; then c=$(texinfo-checksum); w=http://ftp.gnu.org/gnu/texinfo
-	elif [ $$n = unzip     ]; then
-	  c=$(unzip-checksum)
-	  mergenames=0; v=$$(echo $(unzip-version) | sed -e's/\.//')
-	  w=ftp://ftp.info-zip.org/pub/infozip/src/unzip$$v.tgz
-	elif [ $$n = wget      ]; then c=$(wget-checksum); w=http://ftp.gnu.org/gnu/wget
-	elif [ $$n = which     ]; then c=$(which-checksum); w=http://ftp.gnu.org/gnu/which
-	elif [ $$n = xz        ]; then c=$(xz-checksum); w=http://tukaani.org/xz
-	elif [ $$n = zip       ]; then
-	  c=$(zip-checksum)
-	  mergenames=0; v=$$(echo $(zip-version) | sed -e's/\.//')
-	  w=ftp://ftp.info-zip.org/pub/infozip/src/zip$$v.tgz
-	elif [ $$n = zlib      ]; then c=$(zlib-checksum); w=http://www.zlib.net
-	else
-	  echo; echo; echo
-	  echo "'$$n' not recognized as a software tarball name to download."
-	  echo; echo; echo
-	  exit 1
-	fi
+maneage_backup_urls := $(shell awk '!/^#/{printf "%s ", $$1}' \
+                               reproduce/software/config/servers-backup.conf)
+backupservers_all = $(user_backup_urls) $(maneage_backup_urls)
+topbackupserver = $(word 1, $(backupservers_all))
+backupservers = $(filter-out $(topbackupserver),$(backupservers_all))
+
 
-        # Download the raw tarball, using an '.unchecked' suffix to specify
-        # that it is not yet fully checked and usable. But first, since the
-        # download may be interrupted in a previous build and an incomplete
-        # '.unchecked' file may remain, we'll remove any possibly existing
-        # uncheked file.
-	rm -f "$@.unchecked"
-	if [ -f $(DEPENDENCIES-DIR)/$* ]; then
-	  cp $(DEPENDENCIES-DIR)/$* "$@.unchecked"
-	else
-	  if [ $$mergenames = 1 ]; then  tarballurl=$$w/"$*"
-	  else                           tarballurl=$$w
-	  fi
 
-	  echo "Downloading $$tarballurl"
-	  if [ -f $(ibdir)/wget ]; then
-	    downloader="wget --no-use-server-timestamps -O"
-	  else
-	    downloader="$(DOWNLOADER)"
-	  fi
 
-	  touch $(lockdir)/download
-	  $(downloadwrapper) "$$downloader" $(lockdir)/download \
-	                     $$tarballurl "$@.unchecked" "$(backupservers)"
-	fi
 
-        # Make sure the file's Checksum is correct.
-	if type sha512sum > /dev/null 2>/dev/null; then
-	  checksum=$$(sha512sum "$@.unchecked" | awk '{print $$1}')
-	  if [ x"$$checksum" = x"$$c" ]; then
-	    mv "$@.unchecked" "$@"
-	  else
-	    echo "ERROR: Non-matching checksum for '$*'."
-	    echo "Checksum should be: $$c"
-	    echo "Checksum is:        $$checksum"
-	    exit 1
-	  fi
-	else mv "$@.unchecked" "$@"
-	fi
 
 
 
@@ -301,6 +141,10 @@ $(tarballs): $(tdir)/%: | $(lockdir)
 # purpose here, it is very annoying and can cause many complications. We
 # thus remove any part of PATH of that has `ccache' in it before making
 # symbolic links to the programs we are not building ourselves.
+#
+# We'll need the system's PATH for making links to low-level programs we
+# won't be building ourselves.
+syspath := $(PATH)
 makelink = origpath="$$PATH"; \
 	export PATH=$$(echo $(syspath) \
 	                    | tr : '\n' \
@@ -322,7 +166,8 @@ makelink = origpath="$$PATH"; \
 	export PATH="$$origpath"
 
 $(ibdir) $(ildir):; mkdir $@
-$(ibidir)/low-level-links: $(ibidir)/coreutils | $(ibdir) $(ildir)
+$(ibidir)/low-level-links: $(ibidir)/coreutils-$(coreutils-version) \
+                           | $(ibdir) $(ildir)
 
         # Not-installed (but necessary in some cases) compilers.
         #  Clang is necessary for CMake.
@@ -331,6 +176,7 @@ $(ibidir)/low-level-links: $(ibidir)/coreutils | $(ibdir) $(ildir)
 
         # Mac OS specific
 	$(call makelink,mig)
+	$(call makelink,xcrun)
 	$(call makelink,sysctl)
 	$(call makelink,sw_vers)
 	$(call makelink,dsymutil)
@@ -374,17 +220,25 @@ $(ibidir)/low-level-links: $(ibidir)/coreutils | $(ibdir) $(ildir)
 # tarballs of the other compression programs. Once all the compression
 # programs/libraries are complete, we build our own GNU Tar and continue
 # with other software.
-$(ibidir)/gzip: $(tdir)/gzip-$(gzip-version).tar.lz
-	$(call gbuild, gzip-$(gzip-version), static, , V=1) \
-	&& echo "GNU Gzip $(gzip-version)" > $@
+$(lockdir): | $(BDIR); mkdir $@
+$(ibidir)/gzip-$(gzip-version): | $(ibdir) $(ildir) $(lockdir)
+	tarball=gzip-$(gzip-version).tar.lz
+	$(call import-source, $(gzip-url), $(gzip-checksum))
+	$(call gbuild, gzip-$(gzip-version), static, , V=1)
+	echo "GNU Gzip $(gzip-version)" > $@
+
+$(ibidir)/xz-$(xz-version): $(ibidir)/gzip-$(gzip-version)
+	tarball=xz-$(xz-version).tar.gz
+	$(call import-source, $(xz-url), $(xz-checksum))
+	$(call gbuild, xz-$(xz-version), static)
+	echo "XZ Utils $(xz-version)" > $@
 
-$(ibidir)/xz: $(ibidir)/gzip \
-              $(tdir)/xz-$(xz-version).tar.gz
-	$(call gbuild, xz-$(xz-version), static) \
-	&& echo "XZ Utils $(xz-version)" > $@
+$(ibidir)/bzip2-$(bzip2-version): $(ibidir)/gzip-$(gzip-version)
+
+        # Download the tarball.
+	tarball=bzip2-$(bzip2-version).tar.gz
+	$(call import-source, $(bzip2-url), $(bzip2-checksum))
 
-$(ibidir)/bzip2: $(ibidir)/gzip \
-                 $(tdir)/bzip2-$(bzip2-version).tar.gz
         # Bzip2 doesn't have a `./configure' script, and its Makefile
         # doesn't build a shared library. So we can't use the `gbuild'
         # function here and we need to take some extra steps (inspired
@@ -406,71 +260,77 @@ $(ibidir)/bzip2: $(ibidir)/gzip \
 	    makeshared="make -f Makefile-libbz2_so"
 	  fi
 	fi
-	cd $(ddir) && rm -rf $$tdir \
-	&& tar xf $(word 1,$(filter $(tdir)/%,$^)) \
-	&& cd $$tdir \
-	&& sed -e 's@\(ln -s -f \)$$(PREFIX)/bin/@\1@' Makefile \
-	       > Makefile.sed \
-	&& mv Makefile.sed Makefile \
-	&& $$makeshared CC=cc \
-	&& cp -a libbz2* $(ildir)/ \
-	&& make clean \
-	&& $$makecommand CC=cc \
-	&& make install PREFIX=$(idir) \
-	&& cd .. \
-	&& rm -rf $$tdir \
-	&& cd $(ildir) \
-	&& ln -fs libbz2.so.1.0 libbz2.so \
-	&& echo "Bzip2 $(bzip2-version)" > $@
-
-$(ibidir)/unzip: $(ibidir)/gzip \
-                 $(tdir)/unzip-$(unzip-version).tar.gz
+	cd $(ddir)
+	rm -rf $$tdir
+	tar xf $(tdir)/$$tarball
+	cd $$tdir
+	sed -e 's@\(ln -s -f \)$$(PREFIX)/bin/@\1@' Makefile \
+	    > Makefile.sed
+	mv Makefile.sed Makefile
+	$$makeshared CC=cc
+	cp -a libbz2* $(ildir)/
+	make clean
+	$$makecommand CC=cc
+	make install PREFIX=$(idir)
+	cd ..
+	rm -rf $$tdir
+	cd $(ildir)
+	ln -fs libbz2.so.1.0 libbz2.so
+	echo "Bzip2 $(bzip2-version)" > $@
+
+$(ibidir)/unzip-$(unzip-version): $(ibidir)/gzip-$(gzip-version)
+	tarball=unzip-$(unzip-version).tar.gz
 	v=$$(echo $(unzip-version) | sed -e's/\.//')
+	$(call import-source, $(unzip-url), $(unzip-checksum))
 	$(call gbuild, unzip$$v, static,, \
 	               -f unix/Makefile generic \
 	               CFLAGS="-DBIG_MEM -DMMAP",,pwd, \
 	               -f unix/Makefile generic \
-	               BINDIR=$(ibdir) MANDIR=$(idir)/man/man1 ) \
-	&& echo "Unzip $(unzip-version)" > $@
+	               BINDIR=$(ibdir) MANDIR=$(idir)/man/man1 )
+	echo "Unzip $(unzip-version)" > $@
 
-$(ibidir)/zip: $(ibidir)/gzip \
-               $(tdir)/zip-$(zip-version).tar.gz
+$(ibidir)/zip-$(zip-version): $(ibidir)/gzip-$(gzip-version)
+	tarball=zip-$(zip-version).tar.gz
 	v=$$(echo $(zip-version) | sed -e's/\.//')
+	$(call import-source, $(zip-url), $(zip-checksum))
 	$(call gbuild, zip$$v, static,, \
 	               -f unix/Makefile generic \
 	               CFLAGS="-DBIG_MEM -DMMAP",,pwd, \
 	               -f unix/Makefile generic \
-	               BINDIR=$(ibdir) MANDIR=$(idir)/man/man1 ) \
-	&& echo "Zip $(zip-version)" > $@
+	               BINDIR=$(ibdir) MANDIR=$(idir)/man/man1 )
+	echo "Zip $(zip-version)" > $@
 
 # Some programs (like Wget and CMake) that use zlib need it to be dynamic
 # so they use our custom build. So we won't force a static-only build.
 #
 # Note for a static-only build: Zlib's `./configure' doesn't use Autoconf's
 # configure script, it just accepts a direct `--static' option.
-$(ibidir)/zlib: $(ibidir)/gzip \
-                $(tdir)/zlib-$(zlib-version).tar.gz
-	$(call gbuild, zlib-$(zlib-version)) \
-	&& echo "Zlib $(zlib-version)" > $@
+$(ibidir)/zlib-$(zlib-version): $(ibidir)/gzip-$(gzip-version)
+	tarball=zlib-$(zlib-version).tar.gz
+	$(call import-source, $(zlib-url), $(zlib-checksum))
+	$(call gbuild, zlib-$(zlib-version))
+	echo "Zlib $(zlib-version)" > $@
 
 # GNU Tar: When built statically, tar gives a segmentation fault on
 # unpacking Bash. So we'll build it dynamically. Note that technically, zip
 # and unzip aren't dependencies of Tar, but for a clean build, we'll set
 # Tar to be the last compression-related software (the first-set of
 # software to be built).
-$(ibidir)/tar: $(ibidir)/xz \
-               $(ibidir)/zip \
-               $(ibidir)/gzip \
-               $(ibidir)/zlib \
-               $(ibidir)/bzip2 \
-               $(ibidir)/unzip \
-               $(tdir)/tar-$(tar-version).tar.gz
+$(ibidir)/tar-$(tar-version): \
+              $(ibidir)/xz-$(xz-version) \
+              $(ibidir)/zip-$(zip-version) \
+              $(ibidir)/gzip-$(gzip-version) \
+              $(ibidir)/zlib-$(zlib-version) \
+              $(ibidir)/bzip2-$(bzip2-version) \
+              $(ibidir)/unzip-$(unzip-version)
         # Since all later programs depend on Tar, the configuration will be
         # stuck here, only making Tar. So its more efficient to built it on
         # multiple threads (when the user's Make doesn't pass down the
         # number of threads).
-	$(call gbuild, tar-$(tar-version), , , -j$(numthreads) V=1) \
-	&& echo "GNU Tar $(tar-version)" > $@
+	tarball=tar-$(tar-version).tar.gz
+	$(call import-source, $(tar-url), $(tar-checksum))
+	$(call gbuild, tar-$(tar-version), , , -j$(numthreads) V=1)
+	echo "GNU Tar $(tar-version)" > $@
 
 
 
@@ -481,8 +341,34 @@ $(ibidir)/tar: $(ibidir)/xz \
 
 
 
-# Level 2 (SECOND MOST BASIC): Bash and Make
-# ------------------------------------------
+# Level 2 (necessary for linking)
+#
+# Patchelf is necessary for some software on GNU/Linux systems, its job is
+# to manually insert RPATH into the dynamically-linked executable. Since
+# all the other software depend on Pathelf, to avoid manually repeating as
+# a prerequisite (and forgetting in others causing bugs), we'll put it as a
+# dependancy of 'tar'.
+$(ibidir)/patchelf-$(patchelf-version): $(ibidir)/tar-$(tar-version)
+	tarball=patchelf-$(patchelf-version).tar.gz
+	$(call import-source, $(patchelf-url), $(patchelf-checksum))
+	if [ x$(on_mac_os) = xyes ]; then
+	  echo "" > $@
+	else
+	  $(call gbuild, patchelf-$(patchelf-version))
+	  echo "PatchELF $(patchelf-version)" > $@
+	fi
+
+
+
+
+
+
+
+
+
+
+# Level 3 (THIRD MOST BASIC): Bash
+# --------------------------------
 #
 # GNU Make and GNU Bash are the second layer that we'll need to build the
 # basic dependencies.
@@ -492,8 +378,9 @@ $(ibidir)/tar: $(ibidir)/xz \
 # function (for tilde expansion). The first can be disabled with
 # `--disable-load', but unfortunately I don't know any way to fix the
 # second. So, we'll have to build it dynamically for now.
-$(ibidir)/ncurses: $(ibidir)/tar \
-                   $(tdir)/ncurses-$(ncurses-version).tar.gz
+$(ibidir)/ncurses-$(ncurses-version): $(ibidir)/patchelf-$(patchelf-version)
+	tarball=ncurses-$(ncurses-version).tar.gz
+	$(call import-source, $(ncurses-url), $(ncurses-checksum))
 
         # Delete the library that will be installed (so we can make sure
         # the build process completed afterwards and reset the links).
@@ -578,17 +465,14 @@ $(ibidir)/ncurses: $(ibidir)/tar \
 	  exit 1
 	fi
 
-$(ibidir)/readline: $(ibidir)/ncurses \
-                    $(tdir)/readline-$(readline-version).tar.gz
+$(ibidir)/readline-$(readline-version): \
+                   $(ibidir)/ncurses-$(ncurses-version)
+	tarball=readline-$(readline-version).tar.gz
+	$(call import-source, $(readline-url), $(readline-checksum))
 	$(call gbuild, readline-$(readline-version), static, \
 	               --with-curses --disable-install-examples, \
-	               SHLIB_LIBS="-lncursesw" -j$(numthreads)) \
-	&& echo "GNU Readline $(readline-version)" > $@
-
-$(ibidir)/patchelf: $(ibidir)/tar \
-                    $(tdir)/patchelf-$(patchelf-version).tar.gz
-	$(call gbuild, patchelf-$(patchelf-version)) \
-	&& echo "PatchELF $(patchelf-version)" > $@
+	               SHLIB_LIBS="-lncursesw" -j$(numthreads))
+	echo "GNU Readline $(readline-version)" > $@
 
 
 # IMPORTANT: Even though we have enabled `rpath', Bash doesn't write the
@@ -620,16 +504,13 @@ $(ibidir)/patchelf: $(ibidir)/tar \
 #   $ tar cf bash-5.0.$number.tar bash-5.0.$number
 #   $ lzip --best bash-5.0.$number.tar
 #   $ rm -rf bash50-* bash-5.0.$number bash-5.0.tar.gz
+$(ibidir)/bash-$(bash-version): \
+               $(ibidir)/gettext-$(gettext-version) \
+               $(ibidir)/readline-$(readline-version)
 
-ifeq ($(on_mac_os),yes)
-needpatchelf =
-else
-needpatchelf = $(ibidir)/patchelf
-endif
-$(ibidir)/bash: $(needpatchelf) \
-                $(ibidir)/gettext \
-                $(ibidir)/readline \
-                $(tdir)/bash-$(bash-version).tar.lz
+        # Download the tarball.
+	tarball=bash-$(bash-version).tar.lz
+	$(call import-source, $(bash-url), $(bash-checksum))
 
         # Delete the (possibly) existing Bash executable in the project,
         # let it use the default shell of the host.
@@ -655,9 +536,8 @@ $(ibidir)/bash: $(needpatchelf) \
         # default. So, we have to manually include it, currently we are
         # only doing this on GNU/Linux systems (using the `patchelf'
         # program).
-	if [ "x$(needpatchelf)" != x ]; then
-	  if [ -f $(ibdir)/bash ]; then
-	    $(ibdir)/patchelf --set-rpath $(ildir) $(ibdir)/bash; fi
+	if [ -f $(ibdir)/patchelf ]; then
+	  $(ibdir)/patchelf --set-rpath $(ildir) $(ibdir)/bash;
 	fi
 
         # To be generic, some systems use the `sh' command to call the
@@ -668,11 +548,8 @@ $(ibidir)/bash: $(needpatchelf) \
         # Just to be sure that the installation step above went well,
         # before making the link, we'll see if the file actually exists
         # there.
-	if [ -f $(ibdir)/bash ]; then
-	  ln -fs $(ibdir)/bash $(ibdir)/sh
-	  echo "GNU Bash $(bash-version)" > $@
-	else
-	  echo "GNU Bash not built!"; exit 1; fi
+	ln -fs $(ibdir)/bash $(ibdir)/sh
+	echo "GNU Bash $(bash-version)" > $@
 
 
 
@@ -688,46 +565,45 @@ perl-conflddlflags =
 else
 perl-conflddlflags = -Dlddlflags="-shared $$LDFLAGS"
 endif
-$(ibidir)/perl: $(ibidir)/tar \
-                $(tdir)/perl-$(perl-version).tar.gz
+$(ibidir)/perl-$(perl-version): $(ibidir)/patchelf-$(patchelf-version)
+	tarball=perl-$(perl-version).tar.gz
+	$(call import-source, $(perl-url), $(perl-checksum))
 	major_version=$$(echo $(perl-version) \
 	                     | sed -e's/\./ /g' \
 	                     | awk '{printf("%d", $$1)}')
 	base_version=$$(echo $(perl-version) \
 	                     | sed -e's/\./ /g' \
 	                     | awk '{printf("%d.%d", $$1, $$2)}')
-	cd $(ddir) \
-	&& rm -rf perl-$(perl-version) \
-	&& if ! tar xf $(word 1,$(filter $(tdir)/%,$^)); then \
-	      echo; echo "Tar error"; exit 1; \
-	   fi \
-	&& cd perl-$(perl-version) \
-	&& ./Configure -des \
-	               -Dusethreads \
-	               -Duseshrplib \
-	               -Dprefix=$(idir) \
-	               -Dvendorprefix=$(idir) \
-	               -Dprivlib=$(idir)/share/perl$$major_version/core_perl \
-	               -Darchlib=$(idir)/lib/perl$$major_version/$$base_version/core_perl \
-	               -Dsitelib=$(idir)/share/perl$$major_version/site_perl \
-	               -Dsitearch=$(idir)/lib/perl$$major_version/$$basever/site_perl \
-	               -Dvendorlib=$(idir)/share/perl$$major_version/vendor_perl \
-	               -Dvendorarch=$(idir)/lib/perl$$major_version/$$base_version/vendor_perl \
-	               -Dscriptdir=$(idir)/bin/core_perl \
-	               -Dsitescript=$(idir)/bin/site_perl \
-	               -Dvendorscript=$(idir)/bin/vendor_perl \
-	               -Dinc_version_list=none \
-	               -Dman1ext=1perl \
-	               -Dman3ext=3perl \
-	               -Dcccdlflags='-fPIC' \
-	               $(perl-conflddlflags) \
-	               -Dldflags="$$LDFLAGS" \
-	&& make -j$(numthreads) \
-	&& make install \
-	&& cd .. \
-	&& rm -rf perl-$(perl-version) \
-	&& cd $$topdir \
-	&& echo "Perl $(perl-version)" > $@
+	cd $(ddir)
+	rm -rf perl-$(perl-version)
+	tar xf $(tdir)/$$tarball
+	cd perl-$(perl-version)
+	./Configure -des \
+	            -Dusethreads \
+	            -Duseshrplib \
+	            -Dprefix=$(idir) \
+	            -Dvendorprefix=$(idir) \
+	            -Dprivlib=$(idir)/share/perl$$major_version/core_perl \
+	            -Darchlib=$(idir)/lib/perl$$major_version/$$base_version/core_perl \
+	            -Dsitelib=$(idir)/share/perl$$major_version/site_perl \
+	            -Dsitearch=$(idir)/lib/perl$$major_version/$$basever/site_perl \
+	            -Dvendorlib=$(idir)/share/perl$$major_version/vendor_perl \
+	            -Dvendorarch=$(idir)/lib/perl$$major_version/$$base_version/vendor_perl \
+	            -Dscriptdir=$(idir)/bin/core_perl \
+	            -Dsitescript=$(idir)/bin/site_perl \
+	            -Dvendorscript=$(idir)/bin/vendor_perl \
+	            -Dinc_version_list=none \
+	            -Dman1ext=1perl \
+	            -Dman3ext=3perl \
+	            -Dcccdlflags='-fPIC' \
+	            $(perl-conflddlflags) \
+	            -Dldflags="$$LDFLAGS"
+	make -j$(numthreads)
+	make install
+	cd ..
+	rm -rf perl-$(perl-version)
+	cd $$topdir
+	echo "Perl $(perl-version)" > $@
 
 
 
@@ -754,61 +630,70 @@ $(ibidir)/perl: $(ibidir)/tar \
 # an error).
 #
 # Coreutils uses Perl to create man pages!
-$(ibidir)/coreutils: $(ibidir)/bash \
-                     $(ibidir)/perl \
-                     $(ibidir)/openssl \
-                     $(tdir)/coreutils-$(coreutils-version).tar.xz
-	cd $(ddir) \
-	&& rm -rf coreutils-$(coreutils-version) \
-	&& if ! tar xf $(word 1,$(filter $(tdir)/%,$^)); then \
-	      echo; echo "Tar error"; exit 1; \
-	   fi \
-	&& cd coreutils-$(coreutils-version) \
-	&& sed -e's|\#\! /bin/sh|\#\! $(ibdir)/bash|' \
-	       -e's|\#\!/bin/sh|\#\! $(ibdir)/bash|' \
-	       configure > configure-tmp \
-	&& mv configure-tmp configure \
-	&& chmod +x configure \
-	&& ./configure --prefix=$(idir) SHELL=$(ibdir)/bash  \
-	               LDFLAGS="$(LDFLAGS)" CPPFLAGS="$(CPPFLAGS)" \
-	               --disable-silent-rules --with-openssl=yes \
-	&& make SHELL=$(ibdir)/bash -j$(numthreads) \
-	&& make SHELL=$(ibdir)/bash install \
-	&& if [ x$(on_mac_os) != xyes ]; then \
-	     make SHELL=$(ibdir)/bash install DESTDIR=junkinst; \
-	     instprogs=$$(ls junkinst/$(ibdir)); \
-	     for f in $$instprogs; do \
-	       $(ibdir)/patchelf --set-rpath $(ildir) $(ibdir)/$$f; \
-	     done; \
-	     echo "PatchELF applied to all programs."; \
-	   fi \
-	&& cd .. \
-	&& rm -rf coreutils-$(coreutils-version) \
-	&& echo "GNU Coreutils $(coreutils-version)" > $@
+$(ibidir)/coreutils-$(coreutils-version): \
+                    $(ibidir)/bash-$(bash-version) \
+                    $(ibidir)/perl-$(perl-version) \
+                    $(ibidir)/openssl-$(openssl-version)
+
+        # Import, unpack and enter the source directory.
+	tarball=coreutils-$(coreutils-version).tar.xz
+	$(call import-source, $(coreutils-url), $(coreutils-checksum))
+	cd $(ddir)
+	rm -rf coreutils-$(coreutils-version)
+	tar xf $(tdir)/$$tarball
+	cd coreutils-$(coreutils-version)
+
+        # Set the configure script to use our shell, note that we can't
+        # assume GNU SED here yet (it installs after Coreutils).
+	sed -e's|\#\! /bin/sh|\#\! $(ibdir)/bash|' \
+	    -e's|\#\!/bin/sh|\#\! $(ibdir)/bash|' \
+	    configure > configure-tmp
+	mv configure-tmp configure
+	chmod +x configure
+
+        # Configure, build and install Coreutils.
+	./configure --prefix=$(idir) SHELL=$(ibdir)/bash  \
+	            LDFLAGS="$(LDFLAGS)" CPPFLAGS="$(CPPFLAGS)" \
+	            --disable-silent-rules --with-openssl=yes
+	make SHELL=$(ibdir)/bash -j$(numthreads)
+	make SHELL=$(ibdir)/bash install
+
+        # Fix RPATH if necessary.
+	if [ -f $(ibdir)/patchelf ]; then
+	  make SHELL=$(ibdir)/bash install DESTDIR=junkinst
+	  instprogs=$$(ls junkinst/$(ibdir))
+	  for f in $$instprogs; do
+	    $(ibdir)/patchelf --set-rpath $(ildir) $(ibdir)/$$f
+	  done
+	  echo "PatchELF applied to all programs."
+	fi
+
+        # Come back up to the unpacking directory, delete the source
+        # directory and write the final target.
+	cd ..
+	rm -rf coreutils-$(coreutils-version)
+	echo "GNU Coreutils $(coreutils-version)" > $@
 
 # OpenSSL
 #
-# Some programs/libraries later need dynamic linking. So we'll build libssl
-# (and libcrypto) dynamically also.
-#
 # Until we find a nice and generic way to create an updated CA file in the
 # project, the certificates will be available in a file for this project
 # along with the other tarballs.
-#
-# In case you do want a static OpenSSL and libcrypto, then uncomment the
-# following conditional and put $(openssl-static) in the configure options.
-#
-#ifeq ($(static_build),yes)
-#openssl-static = no-dso no-dynamic-engine no-shared
-#endif
 $(idir)/etc:; mkdir $@
-# Note: cert.pm has to be AFTER the tarball, otherwise the build script
-# will try to unpack cert.pm and crash (it unpacks the first dependency
-# under `tdir').
-$(ibidir)/openssl: $(ibidir)/perl \
-                   $(tdir)/openssl-$(openssl-version).tar.gz \
-                   $(tdir)/cert.pem \
-                   | $(idir)/etc
+$(idir)/etc/ssl: | $(idir)/etc; mkdir $@
+$(ibidir)/openssl-$(openssl-version): $(ibidir)/perl-$(perl-version) \
+                  | $(idir)/etc/ssl
+
+        # First download the certificates and copy them into the
+        # installation directory.
+	tarball=cert.pem
+	$(call import-source, $(cert-url), $(cert-checksum))
+	cp $(tdir)/cert.pem $(idir)/etc/ssl/cert.pem
+
+        # Now download the OpenSSL tarball.
+	tarball=openssl-$(openssl-version).tar.gz
+	$(call import-source, $(openssl-url), $(openssl-checksum))
+
         # According to OpenSSL's Wiki (link bellow), it can't automatically
         # detect Mac OS's structure. It will need some help. So we'll use
         # the `on_mac_os' Make variable that we defined in the configure
@@ -816,18 +701,10 @@ $(ibidir)/openssl: $(ibidir)/perl \
         # environment variable.
         #
         # https://wiki.openssl.org/index.php/Compilation_and_Installation
-        #
-        # Bug 58263 (https://savannah.nongnu.org/bugs/?58263): In OpenSSL
-        # Version 1.1.1a (also checked in 1.1.1g), `openssl/ec.h' fails to
-        # include `openssl/openconf.h' on some OSs. The SED hack below
-        # inserts a hardwired element of `openssl/openconf.h' that is
-        # needed to include sections of code `f` that are deprecated in
-        # 1.2.0, but not yet in 1.1.1. This problem may be solved in
-        # version 1.2.x, so please check again in that bug.
-	if [ x$(on_mac_os) = xyes ]; then \
-	  export KERNEL_BITS=64; \
-	  copt="shared no-ssl2 no-ssl3 enable-ec_nistp_64_gcc_128";  \
-	fi; \
+	if [ x$(on_mac_os) = xyes ]; then
+	  export KERNEL_BITS=64
+	  copt="shared no-ssl2 no-ssl3 enable-ec_nistp_64_gcc_128"
+	fi
 	$(call gbuild, openssl-$(openssl-version), , \
 	               zlib \
 	               $$copt \
@@ -835,19 +712,26 @@ $(ibidir)/openssl: $(ibidir)/perl \
 	               --openssldir=$(idir)/etc/ssl \
 	               --with-zlib-lib=$(ildir) \
 	               --with-zlib-include=$(idir)/include, \
-	               -j$(numthreads), , ./config ) \
-	&& mv -v $(idir)/include/openssl/ec.h $(idir)/include/openssl/ec.h.orig \
-	&& sed -e 's,\(# include .openssl/opensslconf\.h.\),\1\n#ifndef DEPRECATEDIN_1_2_0\n#define DEPRECATEDIN_1_2_0(f)   f;\n#endif\n,' \
-	   $(idir)/include/openssl/ec.h.orig > $(idir)/include/openssl/ec.h \
-	&& cp $(tdir)/cert.pem $(idir)/etc/ssl/cert.pem \
-	&& if [ $$? = 0 ]; then \
-	     if [ x$(on_mac_os) = xyes ]; then \
-	       echo "No need to fix rpath in libssl"; \
-	     else \
-	       patchelf --set-rpath $(ildir) $(ildir)/libssl.so; \
-	     fi; \
-	     echo "OpenSSL $(openssl-version)" > $@; \
-	   fi
+	               -j$(numthreads), , ./config )
+
+        # Manually insert RPATH inside the OpenSSL library.
+	if [ -f $(ibdir)/patchelf ]; then
+	   patchelf --set-rpath $(ildir) $(ildir)/libssl.so; \
+	fi
+
+        # Bug 58263 (https://savannah.nongnu.org/bugs/?58263): In OpenSSL
+        # Version 1.1.1a (also checked in 1.1.1g), `openssl/ec.h' fails to
+        # include `openssl/openconf.h' on some OSs. The SED hack below
+        # inserts a hardwired element of `openssl/openconf.h' that is
+        # needed to include sections of code `f` that are deprecated in
+        # 1.2.0, but not yet in 1.1.1. This problem may be solved in
+        # version 1.2.x, so please check again in that bug.
+	mv -v $(idir)/include/openssl/ec.h $(idir)/include/openssl/ec.h.orig
+	sed -e 's,\(# include .openssl/opensslconf\.h.\),\1\n#ifndef DEPRECATEDIN_1_2_0\n#define DEPRECATEDIN_1_2_0(f)   f;\n#endif\n,' \
+	   $(idir)/include/openssl/ec.h.orig > $(idir)/include/openssl/ec.h
+
+        # Build the final target.
+	echo "OpenSSL $(openssl-version)" > $@
 
 
 
@@ -864,8 +748,11 @@ $(ibidir)/openssl: $(ibidir)/perl \
 # them. Note that if it does link with them, the configuration will crash
 # when the library is updated/changed by the host, and the whole purpose of
 # this project is avoid dependency on the host as much as possible.
-$(ibidir)/curl: $(ibidir)/coreutils \
-                $(tdir)/curl-$(curl-version).tar.gz
+$(ibidir)/curl-$(curl-version): $(ibidir)/coreutils-$(coreutils-version)
+
+	tarball=curl-$(curl-version).tar.gz
+	$(call import-source, $(curl-url), $(curl-checksum))
+
 	$(call gbuild, curl-$(curl-version), , \
 	               LIBS="-pthread" \
 	               --with-zlib=$(ildir) \
@@ -882,11 +769,12 @@ $(ibidir)/curl: $(ibidir)/coreutils \
 	               --without-axtls \
 	               --disable-ldaps \
 	               --disable-ldap \
-	               --without-nss, V=1) \
-	&& if [ "x$(needpatchelf)" != x ]; then \
-	     $(ibdir)/patchelf --set-rpath $(ildir) $(ildir)/libcurl.so; \
-	   fi \
-	&& echo "cURL $(curl-version)" > $@
+	               --without-nss, V=1)
+
+	if [ -f $(ibdir)/patchelf ]; then
+	   $(ibdir)/patchelf --set-rpath $(ildir) $(ildir)/libcurl.so
+	fi
+	echo "cURL $(curl-version)" > $@
 
 
 # GNU Wget
@@ -902,13 +790,18 @@ $(ibidir)/curl: $(ibidir)/coreutils \
 # building as part of this project. So to avoid too much dependency on the
 # host system (especially a crash when these libraries are updated on the
 # host), they are disabled here.
-$(ibidir)/wget: $(ibidir)/libiconv \
-                $(ibidir)/coreutils \
-                $(tdir)/wget-$(wget-version).tar.lz
+$(ibidir)/wget-$(wget-version): \
+               $(ibidir)/libiconv-$(libiconv-version) \
+               $(ibidir)/coreutils-$(coreutils-version)
+
+        # Download the tarball.
+	tarball=wget-$(wget-version).tar.lz
+	$(call import-source, $(wget-url), $(wget-checksum))
+
         # We need to explicitly disable `libiconv', because of the
         # `pkg-config' and `libiconv' problem.
-	libs="-pthread"; \
-	if [ x$(needs_ldl) = xyes ]; then libs="$$libs -ldl"; fi; \
+	libs="-pthread"
+	if [ x$(needs_ldl) = xyes ]; then libs="$$libs -ldl"; fi
 	$(call gbuild, wget-$(wget-version), , \
 	               LIBS="$$LIBS $$libs" \
 	               --with-libssl-prefix=$(idir) \
@@ -921,8 +814,8 @@ $(ibidir)/wget: $(ibidir)/libiconv \
 	               --without-libidn \
 	               --disable-pcre2 \
 	               --disable-pcre \
-	               --disable-iri, V=1) \
-	&& echo "GNU Wget $(wget-version)" > $@
+	               --disable-iri, V=1 -j$(numthreads))
+	echo "GNU Wget $(wget-version)" > $@
 
 
 
@@ -937,138 +830,172 @@ $(ibidir)/wget: $(ibidir)/libiconv \
 # process of the higher-level programs and libraries. Note that during the
 # building of those higher-level programs (after this Makefile finishes),
 # there is no access to the system's PATH.
-$(ibidir)/diffutils: $(ibidir)/coreutils \
-                     $(tdir)/diffutils-$(diffutils-version).tar.xz
-	$(call gbuild, diffutils-$(diffutils-version), static,,V=1) \
-	&& echo "GNU Diffutils $(diffutils-version)" > $@
-
-$(ibidir)/file: $(ibidir)/coreutils \
-                $(tdir)/file-$(file-version).tar.gz
-	$(call gbuild, file-$(file-version), static,,V=1) \
-	&& echo "File $(file-version)" > $@
-
-$(ibidir)/findutils: $(ibidir)/coreutils \
-                     $(tdir)/findutils-$(findutils-version).tar.xz
-	$(call gbuild, findutils-$(findutils-version), static,,V=1) \
-	&& echo "GNU Findutils $(findutils-version)" > $@
-
-$(ibidir)/gawk: $(ibidir)/gmp \
-                $(ibidir)/mpfr \
-                $(ibidir)/coreutils \
-                $(tdir)/gawk-$(gawk-version).tar.lz
+$(ibidir)/diffutils-$(diffutils-version): \
+                    $(ibidir)/coreutils-$(coreutils-version)
+	tarball=diffutils-$(diffutils-version).tar.xz
+	$(call import-source, $(diffutils-url), $(diffutils-checksum))
+	$(call gbuild, diffutils-$(diffutils-version), static,,V=1)
+	echo "GNU Diffutils $(diffutils-version)" > $@
+
+$(ibidir)/file-$(file-version): $(ibidir)/coreutils-$(coreutils-version)
+	tarball=file-$(file-version).tar.gz
+	$(call import-source, $(file-url), $(file-checksum))
+	$(call gbuild, file-$(file-version), static,,V=1)
+	echo "File $(file-version)" > $@
+
+$(ibidir)/findutils-$(findutils-version): \
+                    $(ibidir)/coreutils-$(coreutils-version)
+	tarball=findutils-$(findutils-version).tar.xz
+	$(call import-source, $(findutils-url), $(findutils-checksum))
+	$(call gbuild, findutils-$(findutils-version), static,,V=1)
+	echo "GNU Findutils $(findutils-version)" > $@
+
+$(ibidir)/gawk-$(gawk-version): \
+               $(ibidir)/gmp-$(gmp-version) \
+               $(ibidir)/mpfr-$(mpfr-version) \
+               $(ibidir)/coreutils-$(coreutils-version)
+
+        # Download the tarball.
+	tarball=gawk-$(gawk-version).tar.lz
+	$(call import-source, $(gawk-url), $(gawk-checksum))
+
         # AWK doesn't include RPATH by default, so we'll have to manually
         # include it using the `patchelf' program (which was a dependency
         # of Bash). Just note that AWK produces two executables (for
         # example `gawk-4.2.1' and `gawk') and a symbolic link `awk' to one
         # of those executables.
 	$(call gbuild, gawk-$(gawk-version), static, \
-	               --with-readline=$(idir)) \
-	&& if [ "x$(needpatchelf)" != x ]; then \
-	     if [ -f $(ibdir)/gawk ]; then \
-	       $(ibdir)/patchelf --set-rpath $(ildir) $(ibdir)/gawk; \
-	     fi; \
-	     if [ -f $(ibdir)/gawk-$(gawk-version) ]; then \
-	       $(ibdir)/patchelf --set-rpath $(ildir) \
-	                         $(ibdir)/gawk-$(gawk-version); \
-	    fi; \
-	   fi \
-	&& echo "GNU AWK $(gawk-version)" > $@
-
-$(ibidir)/libiconv: $(ibidir)/pkg-config \
-                    $(tdir)/libiconv-$(libiconv-version).tar.gz
-	$(call gbuild, libiconv-$(libiconv-version), static) \
-	&& echo "GNU libiconv $(libiconv-version)" > $@
-
-$(ibidir)/libunistring: $(ibidir)/libiconv \
-                        $(tdir)/libunistring-$(libunistring-version).tar.xz
+	               --with-readline=$(idir))
+
+        # Correct the RPATH on systems that have installed patchelf.
+	if [ -f $(ibdir)/patchelf ]; then
+	  if [ -f $(ibdir)/gawk ]; then
+	    $(ibdir)/patchelf --set-rpath $(ildir) $(ibdir)/gawk
+	  fi
+	  if [ -f $(ibdir)/gawk-$(gawk-version) ]; then
+	    $(ibdir)/patchelf --set-rpath $(ildir) \
+	                      $(ibdir)/gawk-$(gawk-version);
+	  fi
+	fi
+
+        # Build final target.
+	echo "GNU AWK $(gawk-version)" > $@
+
+$(ibidir)/libiconv-$(libiconv-version): \
+                   $(ibidir)/pkg-config-$(pkgconfig-version)
+	tarball=libiconv-$(libiconv-version).tar.gz
+	$(call import-source, $(libiconv-url), $(libiconv-checksum))
+	$(call gbuild, libiconv-$(libiconv-version), static)
+	echo "GNU libiconv $(libiconv-version)" > $@
+
+$(ibidir)/libunistring-$(libunistring-version): \
+                       $(ibidir)/libiconv-$(libiconv-version)
+	tarball=libunistring-$(libunistring-version).tar.xz
+	$(call import-source, $(libunistring-url), $(libunistring-checksum))
 	$(call gbuild, libunistring-$(libunistring-version), static,, \
-	               -j$(numthreads)) \
-	&& echo "GNU libunistring $(libunistring-version)" > $@
+	               -j$(numthreads))
+	echo "GNU libunistring $(libunistring-version)" > $@
 
-$(ibidir)/libxml2: $(ibidir)/tar \
-                   $(tdir)/libxml2-$(libxml2-version).tar.gz
+$(ibidir)/libxml2-$(libxml2-version): $(ibidir)/patchelf-$(patchelf-version)
         # The libxml2 tarball also contains Python bindings which are built
         # and installed to a system directory by default. If you don't need
         # the Python bindings, the easiest solution is to compile without
         # Python support: `./configure --without-python'. If you really need
         # the Python bindings, use `--with-python-install-dir=DIR' instead.
+	tarball=libxml2-$(libxml2-version).tar.gz
+	$(call import-source, $(libxml2-url), $(libxml2-checksum))
 	$(call gbuild, libxml2-$(libxml2-version), static, \
-	               --without-python) \
-	&& echo "Libxml2 $(libxml2-version)" > $@
-
-$(ibidir)/gettext: $(ibidir)/m4 \
-                   $(ibidir)/libxml2 \
-                   $(ibidir)/ncurses \
-                   $(ibidir)/libiconv \
-                   $(ibidir)/libunistring \
-                   $(tdir)/gettext-$(gettext-version).tar.xz
-	$(call gbuild, gettext-$(gettext-version), static, V=1) \
-	&& echo "GNU gettext $(gettext-version)" > $@
-
-$(ibidir)/git: $(ibidir)/curl \
-               $(ibidir)/gettext \
-               $(ibidir)/libiconv \
-               $(tdir)/git-$(git-version).tar.xz
-	if [ x$(on_mac_os) = xyes ]; then \
-	  export LDFLAGS="$$LDFLAGS -lcharset"; \
-	fi; \
+	               --without-python, V=1)
+	echo "Libxml2 $(libxml2-version)" > $@
+
+$(ibidir)/gettext-$(gettext-version): \
+                  $(ibidir)/m4-$(m4-version) \
+                  $(ibidir)/libxml2-$(libxml2-version) \
+                  $(ibidir)/ncurses-$(ncurses-version) \
+                  $(ibidir)/libiconv-$(libiconv-version) \
+                  $(ibidir)/libunistring-$(libunistring-version)
+	tarball=gettext-$(gettext-version).tar.xz
+	$(call import-source, $(gettext-url), $(gettext-checksum))
+	$(call gbuild, gettext-$(gettext-version), static,, \
+	               V=1 -j$(numthreads))
+	echo "GNU gettext $(gettext-version)" > $@
+
+$(ibidir)/git-$(git-version): \
+              $(ibidir)/curl-$(curl-version) \
+              $(ibidir)/gettext-$(gettext-version) \
+              $(ibidir)/libiconv-$(libiconv-version)
+	tarball=git-$(git-version).tar.xz
+	if [ x$(on_mac_os) = xyes ]; then
+	  export LDFLAGS="$$LDFLAGS -lcharset"
+	fi
+	$(call import-source, $(git-url), $(git-checksum))
 	$(call gbuild, git-$(git-version), static, \
 	               --without-tcltk --with-shell=$(ibdir)/bash \
-	               --with-iconv=$(idir), V=1) \
-	&& echo "Git $(git-version)" > $@
-
-$(ibidir)/gmp: $(ibidir)/m4 \
-               $(ibidir)/coreutils \
-               $(tdir)/gmp-$(gmp-version).tar.lz
+	               --with-iconv=$(idir), V=1 -j$(numthreads))
+	echo "Git $(git-version)" > $@
+
+$(ibidir)/gmp-$(gmp-version): \
+              $(ibidir)/m4-$(m4-version) \
+              $(ibidir)/coreutils-$(coreutils-version)
+	tarball=gmp-$(gmp-version).tar.lz
+	$(call import-source, $(gmp-url), $(gmp-checksum))
 	$(call gbuild, gmp-$(gmp-version), static, \
-	               --enable-cxx --enable-fat, ,make check)  \
-	&& echo "GNU Multiple Precision Arithmetic Library $(gmp-version)" > $@
+	               --enable-cxx --enable-fat, \
+	               -j$(numthreads) ,make check)
+	echo "GNU Multiple Precision Arithmetic Library $(gmp-version)" > $@
 
 # On Mac OS, libtool does different things, so to avoid confusion, we'll
 # prefix GNU's libtool executables with `glibtool'.
-$(ibidir)/glibtool: $(ibidir)/m4 \
-                    $(tdir)/libtool-$(libtool-version).tar.xz
+$(ibidir)/libtool-$(libtool-version): $(ibidir)/m4-$(m4-version)
+	tarball=libtool-$(libtool-version).tar.xz
+	$(call import-source, $(libtool-url), $(libtool-checksum))
 	$(call gbuild, libtool-$(libtool-version), static, \
-                       --program-prefix=g, V=1) \
-	&& ln -s $(ibdir)/glibtoolize $(ibdir)/libtoolize \
-	&& echo "GNU Libtool $(libtool-version)" > $@
-
-$(ibidir)/grep: $(ibidir)/coreutils \
-                $(tdir)/grep-$(grep-version).tar.xz
-	$(call gbuild, grep-$(grep-version), static,,V=1) \
-	&& echo "GNU Grep $(grep-version)" > $@
-
-$(ibidir)/libbsd: $(ibidir)/coreutils \
-                  $(tdir)/libbsd-$(libbsd-version).tar.xz
-	$(call gbuild, libbsd-$(libbsd-version), static,,V=1) \
-	&& echo "Libbsd $(libbsd-version)" > $@
+                       --program-prefix=g, V=1 -j$(numthreads))
+	ln -s $(ibdir)/glibtoolize $(ibdir)/libtoolize
+	echo "GNU Libtool $(libtool-version)" > $@
+
+$(ibidir)/grep-$(grep-version): $(ibidir)/coreutils-$(coreutils-version)
+	tarball=grep-$(grep-version).tar.xz
+	$(call import-source, $(grep-url), $(grep-checksum))
+	$(call gbuild, grep-$(grep-version), static,,V=1)
+	echo "GNU Grep $(grep-version)" > $@
+
+$(ibidir)/libbsd-$(libbsd-version): $(ibidir)/coreutils-$(coreutils-version)
+	tarball=libbsd-$(libbsd-version).tar.xz
+	$(call import-source, $(libbsd-url), $(libbsd-checksum))
+	if [ x$(on_mac_os) = xyes ]; then
+	  echo "" > $@
+	else
+	  $(call gbuild, libbsd-$(libbsd-version), static,,V=1)
+	  echo "Libbsd $(libbsd-version)" > $@
+	fi
 
 # We need to apply a patch to the M4 source to be used properly on macOS.
 # The patch [1] was inspired by Homebrew's build instructions [1].
 #
 # [1] https://raw.githubusercontent.com/macports/macports-ports/edf0ee1e2cf/devel/m4/files/secure_snprintf.patch
 # [2] https://github.com/Homebrew/homebrew-core/blob/master/Formula/m4.rb
-$(ibidir)/m4: $(ibidir)/texinfo \
-              $(tdir)/m4-$(m4-version).tar.gz
-	cd $(ddir); \
-	unpackdir=m4-$(m4-version); \
-	rm -rf $$unpackdir \
-	&& if ! tar xf $(word 1,$(filter $(tdir)/%,$^)); then \
-	      echo; echo "Tar error"; exit 1; \
-	   fi \
-	&& cd $$unpackdir \
-	&& if [ x$(on_mac_os) = xyes ]; then \
-	     sed 's|if !(((__GLIBC__ > 2|if !defined(__APPLE__) \&\& !(((__GLIBC__ > 2|' \
-	         lib/vasnprintf.c > lib/vasnprintf_edited.c;  \
-	     mv lib/vasnprintf_edited.c lib/vasnprintf.c; \
-	   fi \
-	&& ./configure --prefix=$(idir) LDFLAGS="$(LDFLAGS)" \
-	               CPPFLAGS="$(CPPFLAGS)" \
-	&& make V=1 -j$(numthreads) \
-	&& make V=1 install \
-	&& cd .. \
-	&& rm -rf $$unpackdir \
-	&& echo "GNU M4 $(m4-version)" > $@
+$(ibidir)/m4-$(m4-version): $(ibidir)/texinfo-$(texinfo-version)
+	tarball=m4-$(m4-version).tar.gz
+	$(call import-source, $(m4-url), $(m4-checksum))
+	cd $(ddir)
+	unpackdir=m4-$(m4-version)
+	rm -rf $$unpackdir
+	tar xf $(tdir)/$$tarball
+	mv m4-* $$unpackdir
+	cd $$unpackdir
+	if [ x$(on_mac_os) = xyes ]; then
+	   sed 's|if !(((__GLIBC__ > 2|if !defined(__APPLE__) \&\& !(((__GLIBC__ > 2|' \
+	       lib/vasnprintf.c > lib/vasnprintf_edited.c
+	   mv lib/vasnprintf_edited.c lib/vasnprintf.c
+	fi
+	./configure --prefix=$(idir) LDFLAGS="$(LDFLAGS)" \
+	            CPPFLAGS="$(CPPFLAGS)"
+	make V=1 -j$(numthreads)
+	make V=1 install
+	cd ..
+	rm -rf $$unpackdir
+	echo "GNU M4 $(m4-version)" > $@
 
 # Metastore is used (through a Git hook) to restore the source modification
 # dates of files after a Git checkout. Another Git hook saves all file
@@ -1087,17 +1014,16 @@ $(ibidir)/m4: $(ibidir)/texinfo \
 #
 # Libbsd is not necessary on macOS systems, because macOS is already a
 # BSD-based distribution. But on GNU/Linux systems, it is necessary.
-ifeq ($(on_mac_os),yes)
-needlibbsd =
-else
-needlibbsd = $(ibidir)/libbsd
-endif
-$(ibidir)/metastore: $(needlibbsd) \
-                     $(ibidir)/sed \
-                     $(ibidir)/git \
-                     $(ibidir)/gawk \
-                     $(ibidir)/coreutils \
-                     $(tdir)/metastore-$(metastore-version).tar.gz
+$(ibidir)/metastore-$(metastore-version): \
+                    $(ibidir)/sed-$(sed-version) \
+                    $(ibidir)/git-$(git-version) \
+                    $(ibidir)/gawk-$(gawk-version) \
+                    $(ibidir)/libbsd-$(libbsd-version) \
+                    $(ibidir)/coreutils-$(coreutils-version)
+
+        # Download the tarball.
+	tarball=metastore-$(metastore-version).tar.gz
+	$(call import-source, $(metastore-url), $(metastore-checksum))
 
         # Metastore doesn't have any `./configure' script. So we'll just
         # call `pwd' as a place-holder for the `./configure' command.
@@ -1114,54 +1040,61 @@ $(ibidir)/metastore: $(needlibbsd) \
         # are currently only available in a fork of `metastore' hosted at:
         # https://github.com/mohammad-akhlaghi/metastore
         #
-        # We want to inform the user if Metastore isn't built, so we don't
-        # continue the call to `gbuild' with an `&&'.
-        #
         # Checking for presence of `.git'. When the project source is
         # downloaded from a non-Git source (for example from arXiv), there
         # is no `.git' directory to work with. So until we find a better
         # solution, avoid the step to to add the Git hooks.
 	current_dir=$$(pwd); \
 	$(call gbuild, metastore-$(metastore-version), static,, \
-	               NO_XATTR=1 V=1,,pwd,PREFIX=$(idir)); \
-	if [ -f $(ibdir)/metastore ]; then \
-	  if [ "x$(needpatchelf)" != x ]; then \
-	    $(ibdir)/patchelf --set-rpath $(ildir) $(ibdir)/metastore; \
-	  fi; \
-	  if [ -d .git ]; then \
-	    user=$$(whoami); \
-	    group=$$(groups | awk '{print $$1}'); \
-	    cd $$current_dir; \
-	    for f in pre-commit post-checkout; do \
+	               NO_XATTR=1 V=1,,pwd,PREFIX=$(idir))
+
+        # Correct RPATH when necessary.
+	if [ -f $(ibdir)/patchelf ]; then
+	  $(ibdir)/patchelf --set-rpath $(ildir) $(ibdir)/metastore
+	fi
+
+        # If this project is being built in a directory version controlled
+        # by Git, copy the hooks into the Git configuation.
+	if [ -f $(ibdir)/metastore ]; then
+	  if [ -d .git ]; then
+	    user=$$(whoami)
+	    group=$$(groups | awk '{print $$1}')
+	    cd $$current_dir
+	    for f in pre-commit post-checkout; do
 	       sed -e's|@USER[@]|'$$user'|g' \
 	           -e's|@GROUP[@]|'$$group'|g' \
 	           -e's|@BINDIR[@]|$(ibdir)|g' \
 	           -e's|@TOP_PROJECT_DIR[@]|'$$current_dir'|g' \
-	           reproduce/software/shell/git-$$f > .git/hooks/$$f \
-	       && chmod +x .git/hooks/$$f; \
-	    done; \
-	  fi \
-	  && echo "Metastore (forked) $(metastore-version)" > $@; \
-	else \
-	  echo; echo; echo; \
-	  echo "*****************"; \
-	  echo "metastore couldn't be installed!"; \
-	  echo; \
-	  echo "Its used for preserving timestamps on Git commits."; \
-	  echo "Its useful for development, not simple running of "; \
-	  echo "the project. So we won't stop the configuration "; \
-	  echo "because it wasn't built."; \
-	  echo "*****************"; \
+	           reproduce/software/shell/git-$$f > .git/hooks/$$f
+	       chmod +x .git/hooks/$$f
+	    done
+	  fi
+	  echo "Metastore (forked) $(metastore-version)" > $@
+	else
+	  echo; echo; echo
+	  echo "*****************"
+	  echo "metastore couldn't be installed!"
+	  echo
+	  echo "Its used for preserving timestamps on Git commits."
+	  echo "Its useful for development, not simple running of "
+	  echo "the project. So we won't stop the configuration "
+	  echo "because it wasn't built."
+	  echo "*****************"
+	  echo "" > $@
 	fi
 
+$(ibidir)/mpfr-$(mpfr-version): $(ibidir)/gmp-$(gmp-version)
+	tarball=mpfr-$(mpfr-version).tar.xz
+	$(call import-source, $(mpfr-url), $(mpfr-checksum))
+	$(call gbuild, mpfr-$(mpfr-version), static, , , make check)
+	echo "GNU Multiple Precision Floating-Point Reliably $(mpfr-version)" > $@
 
-$(ibidir)/mpfr: $(ibidir)/gmp \
-                $(tdir)/mpfr-$(mpfr-version).tar.xz
-	$(call gbuild, mpfr-$(mpfr-version), static, , , make check)  \
-	&& echo "GNU Multiple Precision Floating-Point Reliably $(mpfr-version)" > $@
+$(ibidir)/pkg-config-$(pkgconfig-version): $(ibidir)/patchelf-$(patchelf-version)
+
+        # Download the tarball.
+	tarball=pkg-config-$(pkgconfig-version).tar.gz
+	$(call import-source, $(pkgconfig-url), $(pkgconfig-checksum))
 
-$(ibidir)/pkg-config: $(ibidir)/tar \
-                      $(tdir)/pkg-config-$(pkgconfig-version).tar.gz
         # An existing `libiconv' can cause a conflict with `pkg-config',
         # this is why `libiconv' depends on `pkg-config'. On a clean build,
         # `pkg-config' is built first. But when we don't have a clean build
@@ -1174,32 +1107,36 @@ $(ibidir)/pkg-config: $(ibidir)/tar \
         # (GCC) installed that doesn't support some necessary features of
         # building Glib (as part of pkg-config). So to be safe, for Mac
         # systems, we'll make sure it will use LLVM's Clang.
-	if [ x$(on_mac_os) = xyes ]; then export compiler="CC=clang"; \
-	else                              export compiler=""; \
-	fi; \
+	if [ x$(on_mac_os) = xyes ]; then export compiler="CC=clang"
+	else                              export compiler=""
+	fi
 	$(call gbuild, pkg-config-$(pkgconfig-version), static, \
 	               $$compiler --with-internal-glib \
-	               --with-pc-path=$(ildir)/pkgconfig, V=1) \
-	&& echo "pkg-config $(pkgconfig-version)" > $@
-
-$(ibidir)/sed: $(ibidir)/coreutils \
-               $(tdir)/sed-$(sed-version).tar.xz
-	$(call gbuild, sed-$(sed-version), static,,V=1) \
-	&& echo "GNU Sed $(sed-version)" > $@
-
-$(ibidir)/texinfo: $(ibidir)/perl \
-                   $(tdir)/texinfo-$(texinfo-version).tar.xz
-	$(call gbuild, texinfo-$(texinfo-version), static) \
-	&& if [ "x$(needpatchelf)" != x ]; then \
-	     $(ibdir)/patchelf --set-rpath $(ildir) $(ibdir)/info; \
-	     $(ibdir)/patchelf --set-rpath $(ildir) $(ibdir)/install-info; \
-	   fi \
-	&& echo "GNU Texinfo $(texinfo-version)" > $@
+	               --with-pc-path=$(ildir)/pkgconfig, V=1)
+	echo "pkg-config $(pkgconfig-version)" > $@
+
+$(ibidir)/sed-$(sed-version): $(ibidir)/coreutils-$(coreutils-version)
+	tarball=sed-$(sed-version).tar.xz
+	$(call import-source, $(sed-url), $(sed-checksum))
+	$(call gbuild, sed-$(sed-version), static,,V=1)
+	echo "GNU Sed $(sed-version)" > $@
+
+$(ibidir)/texinfo-$(texinfo-version): \
+                  $(ibidir)/perl-$(perl-version)
+	tarball=texinfo-$(texinfo-version).tar.xz
+	$(call import-source, $(texinfo-url), $(texinfo-checksum))
+	$(call gbuild, texinfo-$(texinfo-version), static)
+	if [ -f $(ibdir)/patchelf ]; then
+	  $(ibdir)/patchelf --set-rpath $(ildir) $(ibdir)/info
+	  $(ibdir)/patchelf --set-rpath $(ildir) $(ibdir)/install-info
+	fi
+	echo "GNU Texinfo $(texinfo-version)" > $@
 
-$(ibidir)/which: $(ibidir)/coreutils \
-                 $(tdir)/which-$(which-version).tar.gz
-	$(call gbuild, which-$(which-version), static) \
-	&& echo "GNU Which $(which-version)" > $@
+$(ibidir)/which-$(which-version): $(ibidir)/coreutils-$(coreutils-version)
+	tarball=/which-$(which-version).tar.gz
+	$(call import-source, $(which-url), $(which-checksum))
+	$(call gbuild, which-$(which-version), static)
+	echo "GNU Which $(which-version)" > $@
 
 
 
@@ -1212,80 +1149,86 @@ $(ibidir)/which: $(ibidir)/coreutils \
 
 # GCC and its prerequisites
 # -------------------------
+$(ibidir)/isl-$(isl-version): $(ibidir)/gmp-$(gmp-version)
+	tarball=isl-$(isl-version).tar.bz2
+	$(call import-source, $(isl-url), $(isl-checksum))
+	if [ $(host_cc) = 1 ]; then
+	  echo "" > $@
+	else
+	  $(call gbuild, isl-$(isl-version), static, , \
+	                 V=1 -j$(numthreads))
+	  echo "GNU Integer Set Library $(isl-version)" > $@
+	fi
 
-$(ibidir)/isl: $(ibidir)/gmp \
-               $(tdir)/isl-$(isl-version).tar.bz2
-	$(call gbuild, isl-$(isl-version), static, , V=1)  \
-	&& echo "GNU Integer Set Library $(isl-version)" > $@
-
-$(ibidir)/mpc: $(ibidir)/mpfr \
-               $(tdir)/mpc-$(mpc-version).tar.gz
-	$(call gbuild, mpc-$(mpc-version), static, , , make check)  \
-	&& echo "GNU Multiple Precision Complex library" > $@
-
-# Binutils' assembler (`as') and linker (`ld') will conflict with other
-# compilers. So until then, on Mac systems we'll use the host opertating
-# system's Binutils equivalents by just making links.
-
-ifeq ($(host_cc),1)
-gcc-prerequisites =
-else
-gcc-prerequisites = $(ibidir)/isl \
-                    $(ibidir)/mpc
-endif
-
-ifeq ($(on_mac_os),yes)
-binutils-tarball =
-else
-binutils-tarball = $(tdir)/binutils-$(binutils-version).tar.lz
-endif
+$(ibidir)/mpc-$(mpc-version): $(ibidir)/mpfr-$(mpfr-version)
+	tarball=mpc-$(mpc-version).tar.gz
+	$(call import-source, $(mpc-url), $(mpc-checksum))
+	if [ $(host_cc) = 1 ]; then
+	  echo "" > $@
+	else
+	  $(call gbuild, mpc-$(mpc-version), static, , \
+	                 -j$(numthreads), make check)
+	  echo "GNU Multiple Precision Complex library" > $@
+	fi
 
 # The installation of Binutils can cause problems during the build of other
 # programs (http://savannah.nongnu.org/bugs/?56294). Therefore, we'll set
 # all other basic programs as Binutils prerequisite and GCC (the final
 # basic target) ultimately just depends on Binutils.
-#
-# The `ld' linker of Binutils needs several `*crt*.o' file to run. On some
-# systems these object files aren't installed in standard places. We
-# defined `LIBRARY_PATH' and that fixed the problem for many
-# systems. However, some software (for example ImageMagick) over-write
-# `LIBRARY_PATH', therefore there is no other way than to put a link to
-# these necessary files in our local build directory. IMPORTANT NOTE:
-# later, when we build the GNU C Library in the project, we should remove
-# this step.
-$(ibidir)/binutils: $(ibidir)/sed \
-                    $(ibidir)/wget \
-                    $(ibidir)/grep \
-                    $(ibidir)/file \
-                    $(ibidir)/gawk \
-                    $(ibidir)/which \
-                    $(ibidir)/glibtool \
-                    $(binutils-tarball) \
-                    $(ibidir)/metastore \
-                    $(ibidir)/findutils \
-                    $(ibidir)/diffutils \
-                    $(ibidir)/coreutils \
-                    $(gcc-prerequisites)
-
-	if [ x$(on_mac_os) = xyes ]; then \
-	  $(call makelink,as); \
-	  $(call makelink,ar); \
-	  $(call makelink,ld); \
-	  $(call makelink,nm); \
-	  $(call makelink,ps); \
-	  $(call makelink,ranlib); \
-	  echo "" > $@; \
-	else \
+$(ibidir)/binutils-$(binutils-version): \
+                   $(ibidir)/sed-$(sed-version) \
+                   $(ibidir)/isl-$(isl-version) \
+                   $(ibidir)/mpc-$(mpc-version) \
+                   $(ibidir)/wget-$(wget-version) \
+                   $(ibidir)/grep-$(grep-version) \
+                   $(ibidir)/file-$(file-version) \
+                   $(ibidir)/gawk-$(gawk-version) \
+                   $(ibidir)/which-$(which-version) \
+                   $(ibidir)/libtool-$(libtool-version) \
+                   $(ibidir)/metastore-$(metastore-version) \
+                   $(ibidir)/findutils-$(findutils-version) \
+                   $(ibidir)/diffutils-$(diffutils-version) \
+                   $(ibidir)/coreutils-$(coreutils-version)
+
+        # Download the tarball.
+	tarball=binutils-$(binutils-version).tar.lz
+	$(call import-source, $(binutils-url), $(binutils-checksum))
+
+        # Binutils' assembler (`as') and linker (`ld') will conflict with
+        # other compilers. So if we don't build our own compiler, we'll use
+        # the host opertating system's equivalents by just making links.
+	if [ x$(on_mac_os) = xyes ]; then
+	  $(call makelink,as)
+	  $(call makelink,ar)
+	  $(call makelink,ld)
+	  $(call makelink,nm)
+	  $(call makelink,ps)
+	  $(call makelink,ranlib)
+	  echo "" > $@
+	else
+
+          # Build binutils with the standard 'gbuild' function.
 	  $(call gbuild, binutils-$(binutils-version), static, \
 	                 --with-lib-path=$(sys_library_path), \
-	                 -j$(numthreads) ) \
-	  && if ! [ x"$(sys_library_path)" = x ]; then \
-	       for f in $(sys_library_path)/*crt*.o; do \
-	         b=$$($(ibdir)/basename $$f); \
-	         ln -s $$f $(ildir)/$$b; \
-	       done; \
-	     fi \
-	  && echo "GNU Binutils $(binutils-version)" > $@; \
+	                 -j$(numthreads) )
+
+          # The `ld' linker of Binutils needs several `*crt*.o' file to
+          # run. On some systems these object files aren't installed in
+          # standard places. We defined `LIBRARY_PATH' and that fixed the
+          # problem for many systems. However, some software (for example
+          # ImageMagick) over-write `LIBRARY_PATH', therefore there is no
+          # other way than to put a link to these necessary files in our
+          # local build directory. IMPORTANT NOTE: later, when we build the
+          # GNU C Library in the project, we should remove this step.
+	  if ! [ x"$(sys_library_path)" = x ]; then
+	    for f in $(sys_library_path)/*crt*.o; do
+	      b=$$($(ibdir)/basename $$f)
+	      ln -s $$f $(ildir)/$$b
+	    done
+	  fi
+
+          # Write the final target.
+	  echo "GNU Binutils $(binutils-version)" > $@
 	fi
 
 # We are having issues with `libiberty' (part of GCC) on Mac. So for now,
@@ -1301,117 +1244,162 @@ $(ibidir)/binutils: $(ibidir)/sed \
 #
 # We are currently having problems installing GCC on macOS, so for the time
 # being, if the project is being run on a macOS, we'll just set a link.
-ifeq ($(host_cc),1)
-gcc-tarball =
-else
-gcc-tarball = $(tdir)/gcc-$(gcc-version).tar.xz
-endif
-$(ibidir)/gcc: $(gcc-tarball) \
-               $(ibidir)/binutils
+$(ibidir)/gcc-$(gcc-version): $(ibidir)/binutils-$(binutils-version)
+
+        # Function to let the users know what to do if build fails.
+	error_message() {
+	    echo; echo
+	    echo "_________________________________________________"
+	    echo "!!!!!!!!       Warning from Maneage      !!!!!!!!"
+	    echo
+	    echo "Unfortunately building of GCC failed on this system!"
+	    echo "Can you please copy the last ~500 lines above and post it"
+	    echo "as a bug here (as an attached file):"
+	    echo "  https://sv.nongnu.org/support/?func=additem&group=reproduce"
+	    echo
+	    echo "In the meantime, please re-configure Maneage with '--host-cc'"
+	    echo "like below so it uses your own C compiler for building the"
+	    echo "high-level software ('-e' is to use the existing configuration):"
+	    echo
+	    echo "  ./project configure -e --host-cc"
+	    echo
+	    echo "__________ SEE NOTE FROM MANEAGE ABOVE __________"
+	    echo; exit 1
+	}
+
+        # Download the tarball.
+	tarball=gcc-$(gcc-version).tar.xz
+	$(call import-source, $(gcc-url), $(gcc-checksum))
 
         # GCC builds is own libraries in '$(idir)/lib64'. But all other
         # libraries are in '$(idir)/lib'. Since this project is only for a
         # single architecture, we can trick GCC into building its libraries
         # in '$(idir)/lib' by defining the '$(idir)/lib64' as a symbolic
         # link to '$(idir)/lib'.
-	if [ $(host_cc) = 1 ]; then \
-	  $(call makelink,cc); \
-	  $(call makelink,cc,,gcc); \
-	  $(call makelink,c++,,g++); \
-	  $(call makelink,gfortran); \
-	  $(call makelink,strip,mandatory); \
-	  ccinfo=$$(gcc --version | awk 'NR==1'); \
-	  echo "C compiler (""$$ccinfo"")" > $@; \
-	else \
-	  current_dir=$$(pwd); \
-	  rm -f $(ibdir)/gcc* $(ibdir)/g++ $(ibdir)/gfortran $(ibdir)/gcov*;\
-	  rm -rf $(ildir)/gcc $(ildir)/libcc* $(ildir)/libgcc*; \
-	  rm -rf $(ildir)/libgfortran* $(ildir)/libstdc* rm $(idir)/x86_64*;\
-	                                 \
-	  ln -fs $(ildir) $(idir)/lib64; \
-	                       \
+	if [ $(host_cc) = 1 ]; then
+
+          # Make sure we don't have any of the program we want to link to
+          # in the '.local/bin' directory.
+	  rm -f $(ibdir)/cc
+	  rm -f $(ibdir)/c++
+	  rm -f $(ibdir)/gcc
+	  rm -f $(ibdir)/cpp
+	  rm -f $(ibdir)/strip;
+	  rm -f $(ibdir)/gfortran;
+
+          # Put links to the host's tools in '.local/bin'.
+	  $(call makelink,cc)
+	  $(call makelink,cpp)
+	  $(call makelink,cc,,gcc)
+	  $(call makelink,gfortran)
+	  $(call makelink,c++,,g++)
+	  $(call makelink,strip,mandatory)
+	  ccinfo=$$(gcc --version | awk 'NR==1')
+	  echo "C compiler (""$$ccinfo"")" > $@
+
+	else
+
+          # We are building GCC, so to avoid any previous build in
+          # '.local/bin', we'll delete all the files that GCC builds from
+          # there.
+	  current_dir=$$(pwd)
+	  rm -f $(ibdir)/gcc* $(ibdir)/g++ $(ibdir)/gfortran $(ibdir)/gcov*
+	  rm -rf $(ildir)/gcc $(ildir)/libcc* $(ildir)/libgcc*
+	  rm -rf $(ildir)/libgfortran* $(ildir)/libstdc* rm $(idir)/x86_64*
+
+          # We don't want '.local/lib' and '.local/lib64' to be separate.
+	  ln -fs $(ildir) $(idir)/lib64
+
+          # By default we'll build GCC in the RAM to avoid building so many
+          # files and possibly harming the hard-drive or SSD. But if the
+          # RAM doesn't have enough space, we can't use it.
 	  in_ram=$$(df $(ddir) \
 	               | awk 'NR==2{print ($$4>10000000) ? "yes" : "no"}'); \
-	  if [ $$in_ram = "yes" ]; then odir=$(ddir); \
-	  else \
-	    odir=$(BDIR)/software/build-tmp-gcc; \
-	    if [ -d $$odir ]; then rm -rf $$odir; fi; \
-	    mkdir $$odir; \
-	  fi; \
-	  cd $$odir; \
-	  rm -rf gcc-$(gcc-version); \
-	  tar xf $(word 1,$(filter $(tdir)/%,$^)); \
-	  if [ $$odir != $(ddir) ]; then \
-	    ln -s $$odir/gcc-$(gcc-version) $(ddir)/gcc-$(gcc-version); \
-	  fi; \
-	  if cd gcc-$(gcc-version) \
-	  && mkdir build \
-	  && cd build \
-	  && ../configure SHELL=$(ibdir)/bash \
-	                  --prefix=$(idir) \
-	                  --with-mpc=$(idir) \
-	                  --with-gmp=$(idir) \
-	                  --with-isl=$(idir) \
-	                  --with-mpfr=$(idir) \
-	                  --with-local-prefix=$(idir) \
-	                  --with-build-time-tools=$(idir) \
-	                  --enable-lto \
-	                  --enable-shared \
-	                  --enable-cet=auto \
-	                  --enable-default-pie \
-	                  --enable-default-ssp \
-	                  --enable-decimal-float \
-	                  --enable-threads=posix \
-	                  --enable-languages=c,c++,fortran,objc,obj-c++ \
-	                  --disable-nls \
-	                  --disable-libada \
-	                  --disable-multilib \
-	                  --disable-multiarch \
-	  && make SHELL=$(ibdir)/bash -j$(numthreads) \
-	  && make SHELL=$(ibdir)/bash install \
-	  && cd ../.. \
-	  && tempname=$$odir/gcc-$(gcc-version)/build/rpath-temp-copy \
-	  && if [ "x$(on_mac_os)" != xyes ]; then \
-	       for f in $$(find $(idir)/libexec/gcc) $(ildir)/libstdc++*; do \
-	         isdynamic=$$(file $$f | grep "dynamically linked"); \
-	         if [ x"$$isdynamic" != x ]; then \
-	           cp $$f $$tempname; \
-	           patchelf --set-rpath $(ildir) $$tempname; \
-	           echo "$$f: added rpath"; \
-	           islibcpp=$$(echo $$f | grep "libstdc++"); \
-	           if [ x"$$islibcpp" != x ]; then \
-	             patchelf --add-needed $(ildir)/libiconv.so $$tempname; \
-	             echo "$$f: linked with libiconv"; \
-	           fi; \
-	           mv $$tempname $$f; \
-	         fi; \
-	       done; \
-	     fi \
-	  && rm -rf gcc-$(gcc-version) \
-	  && cd $$current_dir \
-	  && if [ "$$odir" != "$(ddir)" ]; then \
-	       rm -rf $$odir; \
-	       rm $(ddir)/gcc-$(gcc-version); \
-	     fi \
-	  && ln -sf $(ibdir)/gcc $(ibdir)/cc; \
-	  then \
-	    echo "GNU Compiler Collection (GCC) $(gcc-version)" > $@; \
-	  else echo; echo; echo; \
-	    echo "_________________________________________________"; \
-	    echo "!!!!!!!!       Warning from Maneage      !!!!!!!!"; \
-	    echo; \
-	    echo "Unfortunately building of GCC failed on this system!"; \
-	    echo "Can you please copy the last ~500 lines above and post it"; \
-	    echo "as a bug here (as an attached file):"; \
-	    echo "  https://sv.nongnu.org/support/?func=additem&group=reproduce"; \
-	    echo; \
-	    echo "In the meantime, please re-configure Maneage with '--host-cc'"; \
-	    echo "like below so it uses your own C compiler for building the"; \
-	    echo "high-level software ('-e' is to use the existing configuration):"; \
-	    echo; \
-	    echo "  ./project configure -e --host-cc"; \
-	    echo; \
-	    echo "__________ SEE NOTE FROM MANEAGE ABOVE __________"; \
-	    echo; exit 1; \
-	  fi; \
+	  if [ $$in_ram = "yes" ]; then odir=$(ddir)
+	  else
+	    odir=$(BDIR)/software/build-tmp-gcc
+	    if [ -d $$odir ]; then rm -rf $$odir; fi
+	    mkdir $$odir
+	  fi
+
+          # Go into the proper directory, unpack GCC and prepare the
+          # 'build' directory inside it for all the built files.
+	  cd $$odir
+	  rm -rf gcc-$(gcc-version)
+	  tar xf $(tdir)/$$tarball
+	  if [ $$odir != $(ddir) ]; then
+	    ln -s $$odir/gcc-$(gcc-version) $(ddir)/gcc-$(gcc-version)
+	  fi
+	  cd gcc-$(gcc-version)
+	  mkdir build
+	  cd build
+
+          # Configure, build and install GCC, if any of three steps fails,
+          # the error message will be printed.
+	  if ! ../configure SHELL=$(ibdir)/bash \
+	                    --prefix=$(idir) \
+	                    --with-mpc=$(idir) \
+	                    --with-gmp=$(idir) \
+	                    --with-isl=$(idir) \
+	                    --with-mpfr=$(idir) \
+	                    --with-local-prefix=$(idir) \
+	                    --with-build-time-tools=$(idir) \
+	                    --enable-lto \
+	                    --enable-shared \
+	                    --enable-cet=auto \
+	                    --enable-default-pie \
+	                    --enable-default-ssp \
+	                    --enable-decimal-float \
+	                    --enable-threads=posix \
+	                    --enable-languages=c,c++,fortran,objc,obj-c++ \
+	                    --disable-nls \
+	                    --disable-libada \
+	                    --disable-multilib \
+	                    --disable-multiarch; then error_message; fi
+	  if ! make SHELL=$(ibdir)/bash -j$(numthreads); then error_message; fi
+	  if ! make SHELL=$(ibdir)/bash install; then error_message; fi
+
+          # We need to manually fix the RPATH inside GCC's libraries, the
+          # programs built by GCC already have RPATH.
+	  tempname=$$odir/gcc-$(gcc-version)/build/rpath-temp-copy
+	  if [ -f $(ibdir)/patchelf ]; then
+
+            # Go over all the installed GCC libraries (its executables are
+            # fine!).
+	    for f in $$(find $(idir)/libexec/gcc -type f) $(ildir)/libstdc++*; do
+
+              # Make sure this is a static library, copy it to a temporary
+              # name (to avoid any possible usage of the file while it is
+              # being corrected), and add RPATH inside of it and put the
+              # corrected file back in its place. In the case of the
+              # standard C++ library, we also need to manually insert a
+              # linking to libiconv.
+	      if file $$f | grep -q "dynamically linked"; then
+	        cp $$f $$tempname
+	        patchelf --set-rpath $(ildir) $$tempname
+	        echo "$$f: added rpath"
+	        if echo $$f | grep -q "libstdc++"; then
+	          patchelf --add-needed $(ildir)/libiconv.so $$tempname
+	          echo "$$f: linked with libiconv"
+	        fi
+	        mv $$tempname $$f
+	      fi
+	    done
+	  fi
+
+          # Come back up to the un-packing directory and delete the GCC
+          # source directory.
+	  cd ../..
+	  rm -rf gcc-$(gcc-version)
+	  cd $$current_dir
+	  if [ "$$odir" != "$(ddir)" ]; then
+	    rm -rf $$odir;
+	    rm $(ddir)/gcc-$(gcc-version);
+	  fi
+
+          # Set 'cc' to point to 'gcc'.
+	  ln -sf $(ibdir)/gcc $(ibdir)/cc
+
+          # Write the final target.
+	  echo "GNU Compiler Collection (GCC) $(gcc-version)" > $@
 	fi
diff --git a/reproduce/software/make/build-rules.mk b/reproduce/software/make/build-rules.mk
index 260ded8..7471e5b 100644
--- a/reproduce/software/make/build-rules.mk
+++ b/reproduce/software/make/build-rules.mk
@@ -1,7 +1,7 @@
 # Generic configurable recipes to build packages with GNU Build system or
 # CMake. This is Makefile is not intended to be run directly, it will be
-# imported into `basic.mk' and `high-level.mk'. They should be activated
-# with Make's `Call' function.
+# imported into 'basic.mk' and 'high-level.mk'. They should be activated
+# with Make's 'Call' function.
 #
 # Copyright (C) 2018-2020 Mohammad Akhlaghi <mohammad@akhlaghi.org>
 #
@@ -22,31 +22,84 @@
 
 
 
-# IMPORTANT note
-# --------------
+# Import/download project's source
+# --------------------------------
 #
-# Without using `&&', if a step fails, the process will continue. However,
-# in the `if' statements, we need `;' (particularly between `]' and
-# `then'). So we need to put any necessary checks at the start, then when
-# we start the process, every command will be separated by an `&&'.
+# Copy/Download the raw tarball into an '.unchecked' suffix. Then calculate
+# its checksum and if it is correct, remove the extra suffix.
+#
+# Arguments:
+#   1: The optional URL to use for this tarball.
+#   2: The expeced checksum of the tarball.
+#
+# Necessary shell variables
+#   'tarball': This is the name of the actual tarball file without a
+#   directory.
+import-source = final=$(tdir)/$$tarball; \
+	url=$(strip $(1)); \
+	exp_checksum="$(strip $(2))"; \
+	if [ -f $$final ]; then \
+	  echo "$(tdir)/$$tarball: already present in project."; \
+	else \
+	  unchecked="$$final.unchecked"; \
+	  rm -f "$$unchecked"; \
+	  if [ -f $(DEPENDENCIES-DIR)/$$tarball ]; then \
+	    cp $(DEPENDENCIES-DIR)/$$tarball "$$unchecked"; \
+	  else \
+	    if [ x"$$url" = x ]; then \
+	      bservers="$(backupservers)"; \
+	      tarballurl=$(topbackupserver)/$$tarball; \
+	    else \
+	      bservers="$(backupservers_all)"; \
+	      tarballurl=$$url/$$tarball; \
+	    fi; \
+	    if [ -f $(ibdir)/wget ]; then \
+	      downloader="wget --no-use-server-timestamps -O"; \
+	    else \
+	      downloader="$(DOWNLOADER)"; \
+	    fi; \
+	    touch $(lockdir)/download; \
+	    $(downloadwrapper) "$$downloader" $(lockdir)/download \
+	                       $$tarballurl "$$unchecked" "$$bservers"; \
+	  fi; \
+	  if [ x"$$exp_checksum" = x"NO-CHECK-SUM" ]; then \
+	    mv "$$unchecked" "$$final"; \
+	  else \
+	    if type sha512sum > /dev/null 2>/dev/null; then \
+	      checksum=$$(sha512sum "$$unchecked" | awk '{print $$1}'); \
+	      if [ x"$$checksum" = x"$$exp_checksum" ]; then \
+	        mv "$$unchecked" "$$final"; \
+	      else \
+	        echo "ERROR: Non-matching checksum for '$$tarball'."; \
+	        echo "Checksum should be: $$exp_checksum"; \
+	        echo "Checksum is:        $$checksum"; \
+	        exit 1; \
+	      fi; \
+	    else mv "$$unchecked" "$$final"; \
+	    fi; \
+	  fi; \
+	fi
 
 
 
 
 
+# Unpack a tarball
+# ----------------
+#
 # Unpack a tarball in the current directory. The issue is that until we
 # install GNU Tar within Maneage, we have to use the host's Tar
 # implementation and in some cases, they don't recognize '.lz'.
-uncompress = csuffix=$$(echo $$tarball \
+uncompress = csuffix=$$(echo $$utarball \
 	                     | sed -e's/\./ /g' \
 	                     | awk '{print $$NF}'); \
 	if [ x$$csuffix = xlz ]; then \
 	  intarrm=1; \
-	  intar=$$(echo $$tarball | sed -e's/.lz//'); \
-	  lzip -c -d $$tarball > $$intar; \
+	  intar=$$(echo $$utarball | sed -e's/.lz//'); \
+	  lzip -c -d $$utarball > $$intar; \
 	else \
 	  intarrm=0; \
-	  intar=$$tarball; \
+	  intar=$$utarball; \
 	fi; \
 	if tar xf $$intar; then \
 	  if [ x$$intarrm = x1 ]; then rm $$intar; fi; \
@@ -64,20 +117,20 @@ uncompress = csuffix=$$(echo $$tarball \
 #
 # Arguments:
 #  1: Directory name after unpacking.
-#  2: Set to `static' for a static build.
+#  2: Set to 'static' for a static build.
 #  3: Extra configuration options.
 #  4: Extra options/arguments to pass to Make.
-#  5: Step to run between `make' and `make install': usually `make check'.
-#  6: The configuration script (`configure' by default).
-#  7: Arguments for `make install'.
+#  5: Step to run between 'make' and 'make install': usually 'make check'.
+#  6: The configuration script ('configure' by default).
+#  7: Arguments for 'make install'.
 #
-# NOTE: Unfortunately the configure script of `zlib' doesn't recognize
-# `SHELL'. So we'll have to remove it from the call to the configure
+# NOTE: Unfortunately the configure script of 'zlib' doesn't recognize
+# 'SHELL'. So we'll have to remove it from the call to the configure
 # script.
 #
 # NOTE: A program might not contain any configure script. In this case,
-# we'll just pass a non-relevant function like `pwd'. So SED should be used
-# to modify `confscript' or to set `configop'.
+# we'll just pass a non-relevant function like 'pwd'. So SED should be used
+# to modify 'confscript' or to set 'configop'.
 gbuild = if [ x$(static_build) = xyes ] && [ "x$(2)" = xstatic ]; then \
 	   export LDFLAGS="$$LDFLAGS -static"; \
 	 fi; \
@@ -85,9 +138,8 @@ gbuild = if [ x$(static_build) = xyes ] && [ "x$(2)" = xstatic ]; then \
 	 if [ x"$$check" = x ]; then check="echo Skipping-check"; fi; \
 	 cd $(ddir); \
 	 rm -rf $(1); \
-	 if [ x"$$gbuild_tar" = x ]; then \
-	   tarball=$(word 1,$(filter $(tdir)/%,$^)); \
-	 else tarball=$$gbuild_tar; \
+	 if [ x"$$gbuild_tar" = x ]; then utarball=$(tdir)/$$tarball; \
+	 else                             utarball=$$gbuild_tar;      \
 	 fi; \
 	 $(call uncompress); \
 	 cd $(1); \
@@ -95,7 +147,7 @@ gbuild = if [ x$(static_build) = xyes ] && [ "x$(2)" = xstatic ]; then \
 	 if   [ x"$(strip $(6))" = x ]; then confscript=./configure; \
 	 else confscript="$(strip $(6))"; \
 	 fi; \
-             \
+	     \
 	 if   [ -f $(ibdir)/bash ]; then \
 	   if [ -f "$$confscript" ]; then \
 	     sed -e's|\#\! /bin/sh|\#\! $(ibdir)/bash|' \
@@ -108,7 +160,7 @@ gbuild = if [ x$(static_build) = xyes ] && [ "x$(2)" = xstatic ]; then \
 	 elif [ -f /bin/bash ]; then shellop="SHELL=/bin/bash"; \
 	 else shellop="SHELL=/bin/sh"; \
 	 fi; \
-             \
+	     \
 	 if [ -f "$$confscript" ]; then \
 	   if [ x"$(strip $(1))" = x"zlib-$(zlib-version)" ]; then \
 	     configop="--prefix=$(idir)"; \
@@ -118,12 +170,12 @@ gbuild = if [ x$(static_build) = xyes ] && [ "x$(2)" = xstatic ]; then \
 	     \
 	 echo; echo "Using '$$confscript' to configure:"; echo; \
 	 echo "$$confscript $(3) $$configop"; echo; \
-	 $$confscript $(3) $$configop \
-	 && make "$$shellop" $(4) \
-	 && $$check \
-	 && make "$$shellop" install $(7) \
-	 && cd .. \
-	 && rm -rf $(1)
+	 $$confscript $(3) $$configop; \
+	 make "$$shellop" $(4); \
+	 $$check; \
+	 make "$$shellop" install $(7); \
+	 cd ..; \
+	 rm -rf $(1)
 
 
 
@@ -131,7 +183,7 @@ gbuild = if [ x$(static_build) = xyes ] && [ "x$(2)" = xstatic ]; then \
 # CMake
 # -----
 #
-# According to the link below, in CMake `/bin/sh' is hardcoded, so there is
+# According to the link below, in CMake '/bin/sh' is hardcoded, so there is
 # no way to change it unfortunately!
 #
 # https://stackoverflow.com/questions/21167014/how-to-set-shell-variable-in-makefiles-generated-by-cmake
@@ -139,17 +191,18 @@ cbuild = if [ x$(static_build) = xyes ] && [ $(2)x = staticx ]; then \
 	   export LDFLAGS="$$LDFLAGS -static"; \
 	   opts="-DBUILD_SHARED_LIBS=OFF"; \
 	 fi; \
-	 tarball=$(word 1,$(filter $(tdir)/%,$^)); \
 	 cd $(ddir); \
 	 rm -rf $(1); \
+	 utarball=$(tdir)/$$tarball; \
 	 $(call uncompress); \
-	 cd $(1) \
-	 && rm -rf project-build \
-	 && mkdir project-build \
-	 && cd project-build \
-	 && cmake .. -DCMAKE_LIBRARY_PATH=$(ildir) \
-	             -DCMAKE_INSTALL_PREFIX=$(idir) \
-	             -DCMAKE_VERBOSE_MAKEFILE:BOOL=ON $$opts $(3) \
-	 && make && make install \
-	 && cd ../.. \
-	 && rm -rf $(1)
+	 cd $(1); \
+	 rm -rf project-build; \
+	 mkdir project-build; \
+	 cd project-build; \
+	 cmake .. -DCMAKE_LIBRARY_PATH=$(ildir) \
+	          -DCMAKE_INSTALL_PREFIX=$(idir) \
+	          -DCMAKE_VERBOSE_MAKEFILE:BOOL=ON $$opts $(3); \
+	 make; \
+	 make install; \
+	 cd ../..; \
+	 rm -rf $(1)
diff --git a/reproduce/software/make/high-level.mk b/reproduce/software/make/high-level.mk
index 75fa8ac..b756cb9 100644
--- a/reproduce/software/make/high-level.mk
+++ b/reproduce/software/make/high-level.mk
@@ -4,7 +4,11 @@
 #                      !!!!! IMPORTANT NOTES !!!!!
 #
 # This Makefile will be run by the initial `./project configure' script. It
-# is not included into the reproduction pipe after that.
+# is not included into the project afterwards.
+#
+# This Makefile builds the high-level (optional) software in Maneage that
+# users can choose for different projects. It thus assumes that the
+# low-level tools (like GNU Tar and etc) are already build by 'basic.mk'.
 #
 # ------------------------------------------------------------------------
 #
@@ -24,35 +28,82 @@
 # You should have received a copy of the GNU General Public License
 # along with this Makefile.  If not, see <http://www.gnu.org/licenses/>.
 
-
-
-# Top level environment
+# Top level environment (same as 'basic.mk')
 include reproduce/software/config/LOCAL.conf
 include reproduce/software/make/build-rules.mk
-include reproduce/software/config/TARGETS.conf
 include reproduce/software/config/versions.conf
 include reproduce/software/config/checksums.conf
+
+# The optional URLs of software. Note that these may need the software
+# version, so it is important that they be loaded after 'versions.conf'.
+include reproduce/software/config/urls.conf
+
+# Configurations specific to this Makefile
+include reproduce/software/config/TARGETS.conf
 include reproduce/software/config/texlive-packages.conf
 
+# Basic directories (similar to 'basic.mk').
 lockdir = $(BDIR)/locks
 tdir    = $(BDIR)/software/tarballs
 ddir    = $(BDIR)/software/build-tmp
 idir    = $(BDIR)/software/installed
 ibdir   = $(BDIR)/software/installed/bin
 ildir   = $(BDIR)/software/installed/lib
-iidir   = $(BDIR)/software/installed/include
-dtexdir = $(shell pwd)/reproduce/software/bibtex
-patchdir= $(shell pwd)/reproduce/software/patches
-itidir  = $(BDIR)/software/installed/version-info/tex
-ictdir  = $(BDIR)/software/installed/version-info/cite
-ipydir  = $(BDIR)/software/installed/version-info/python
 ibidir  = $(BDIR)/software/installed/version-info/proglib
 
-# Set the top-level software to build.
-all: $(foreach p, $(top-level-programs),  $(ibidir)/$(p)) \
-     $(foreach p, $(top-level-python),    $(ipydir)/$(p)) \
+# Basic directories (specific to this Makefile).
+iidir    = $(BDIR)/software/installed/include
+shsrcdir = $(shell pwd)/reproduce/software/shell
+dtexdir  = $(shell pwd)/reproduce/software/bibtex
+patchdir = $(shell pwd)/reproduce/software/patches
+itidir   = $(BDIR)/software/installed/version-info/tex
+ictdir   = $(BDIR)/software/installed/version-info/cite
+ipydir   = $(BDIR)/software/installed/version-info/python
+
+# Targets to build.
+ifeq ($(strip $(all_highlevel)),1)
+
+  # Set it to build all programs. Pay attention to special software:
+  #
+  # Versions as variables (for example minizip): they have the same as the
+  # version as others and the version number is actually a variable. So
+  # we'll need to filter it out, then add it in the end: minizip (has same
+  # version as zlib)
+  #
+  # Packages that are installed in the same recipe as others. These need to
+  # be totally removed when testing all the builds (they will be built
+  # anyway).  lapack (installed with ATLAS)
+  targets-proglib := $(filter-out minizip-% lapack-%, \
+      $(shell awk '/^# CLASS:PYTHON/{good=0} \
+                   good==1 && !/^#/ && $$1 ~ /-version$$/ { \
+                       printf("%s %s ", $$1, $$3)} \
+                   /^# CLASS:HIGHLEVEL/{good=1}' \
+                  reproduce/software/config/versions.conf \
+              | sed 's/version //g')) \
+      minizip-$(minizip-version)
+
+  # List all existing Python packages.
+  targets-python := $(shell \
+    awk '/^# CLASS:PYTHON/{good=1} \
+         good==1 && !/^#/ && $$1 ~ /-version$$/ {printf("%s %s ",$$1,$$3)}' \
+        reproduce/software/config/versions.conf | sed 's/version //g')
+else
+
+  # Append the version of each software to its name. We are using a Make
+  # feature where a variable name is defined with another variable.
+  targets-python := $(foreach p,$(top-level-python),$(p)-$($(p)-version))
+  targets-proglib := $(foreach p,$(top-level-programs),$(p)-$($(p)-version))
+
+endif
+
+# Ultimate Makefile target.
+all: $(foreach p, $(targets-proglib), $(ibidir)/$(p)) \
+     $(foreach p, $(targets-python), $(ipydir)/$(p)) \
      $(itidir)/texlive
 
+# Define the shell environment
+# ----------------------------
+#
 # Other basic environment settings: We are only including the host
 # operating system's PATH environment variable (after our own!) for the
 # compiler and linker. For the library binaries and headers, we are only
@@ -67,18 +118,28 @@ all: $(foreach p, $(top-level-programs),  $(ibidir)/$(p)) \
 #
 #    2) Add `--noprofile --norc' to `.SHELLFLAGS' so doesn't load the
 #       user's environment.
+#
+# Shell settings similar to 'basic.mk':
 .ONESHELL:
-.SHELLFLAGS := --noprofile --norc -ec
-export CCACHE_DISABLE := 1
 export PATH := $(ibdir)
+export CCACHE_DISABLE := 1
+export SHELL := $(ibdir)/bash
+export CPPFLAGS := -I$(idir)/include
+.SHELLFLAGS := --noprofile --norc -ec
+export PKG_CONFIG_PATH := $(ildir)/pkgconfig
+export LDFLAGS := $(rpath_command) -L$(ildir)
+export PKG_CONFIG_LIBDIR := $(ildir)/pkgconfig
+
+# Settings specific to this Makefile.
 export CC := $(ibdir)/gcc
 export CXX := $(ibdir)/g++
-export SHELL := $(ibdir)/bash
 export F77 := $(ibdir)/gfortran
 export LD_RUN_PATH := $(ildir):$(il64dir)
-export PKG_CONFIG_PATH := $(ildir)/pkgconfig
 export LD_LIBRARY_PATH := $(ildir):$(il64dir)
-export PKG_CONFIG_LIBDIR := $(ildir)/pkgconfig
+
+# Recipe startup script, see `reproduce/software/shell/bashrc.sh'.
+export PROJECT_STATUS := configure_highlevel
+export BASH_ENV := $(shell pwd)/reproduce/software/shell/bashrc.sh
 
 # Until we build our own C library, without this, our GCC won't be able to
 # compile anything! Note that on most systems (in particular
@@ -97,282 +158,45 @@ export DYLD_LIBRARY_PATH :=
 # for `ld'.
 export LIBRARY_PATH := $(sys_library_path)
 
-# Recipe startup script, see `reproduce/software/shell/bashrc.sh'.
-export PROJECT_STATUS := configure_highlevel
-export BASH_ENV := $(shell pwd)/reproduce/software/shell/bashrc.sh
-
-# Servers to use as backup, later this should go in a file that is not
-# under version control (the actual server that the tarbal comes from is
-# irrelevant).
-backupservers := $(shell awk '!/^#/{printf "%s ", $$1}' \
-                         reproduce/software/config/servers-backup.conf)
-
 # Building flags:
 #
 # C++ flags: when we build GCC, the C++ standard library needs to link with
 # libiconv. So it is necessary to generically include `-liconv' for all C++
 # builds.
-export CPPFLAGS          := -I$(idir)/include
-export LDFLAGS           := $(rpath_command) -L$(ildir)
 ifeq ($(host_cc),0)
 export CXXFLAGS          := -liconv
 endif
 
-
-
-
-
-# We want the download to happen on a single thread. So we need to define a
-# lock, and call a special script we have written for this job. These are
-# placed here because we want them both in the `high-level.mk' and
-# `python.mk'.
-$(lockdir): | $(BDIR); mkdir $@
-downloader="wget --no-use-server-timestamps -O";
+# Servers to use as backup. Maneage already has some fixed servers that can
+# be used to download software tarballs. They are in a configuation
+# file. But we give precedence to the "user" backup servers.
+#
+# One important "user" server (which the user doesn't actually give, but is
+# found at configuration time in 'configure.sh') is Zenodo (see the
+# description in 'configure.sh' for more on why this depends on
+# configuration time).
+#
+# Afer putting everything together, we use the first server as the
+# reference for all software if their '-url' variable isn't defined (in
+# 'reproduce/software/config/urls.conf').
 downloadwrapper = ./reproduce/analysis/bash/download-multi-try
+maneage_backup_urls := $(shell awk '!/^#/{printf "%s ", $$1}' \
+                               reproduce/software/config/servers-backup.conf)
+backupservers_all = $(user_backup_urls) $(maneage_backup_urls)
+topbackupserver = $(word 1, $(backupservers_all))
+backupservers = $(filter-out $(topbackupserver),$(backupservers_all))
 
 
 
 
 
-# Mini-environment software
+# Import rules to build Python packages,
 include reproduce/software/make/python.mk
 
 
 
 
 
-# Tarballs
-# --------
-#
-# All the necessary tarballs are defined and prepared with this rule.
-#
-# Note that we want the tarballs to follow the convention of NAME-VERSION
-# before the `tar.XX' prefix. For those programs that don't follow this
-# convention, but include the name/version in their tarball names with
-# another format, we'll do the modification before the download so the
-# downloaded file has our desired format.
-tarballs = $(foreach t, apachelog4cxx-$(apachelog4cxx-version).tar.lz \
-                        apr-$(apr-version).tar.gz \
-                        apr-util-$(apr-util-version).tar.gz \
-                        astrometry.net-$(astrometrynet-version).tar.gz \
-                        atlas-$(atlas-version).tar.bz2 \
-                        autoconf-$(autoconf-version).tar.lz \
-                        automake-$(automake-version).tar.gz \
-                        bison-$(bison-version).tar.xz \
-                        boost-$(boost-version).tar.gz \
-                        cairo-$(cairo-version).tar.xz \
-                        cdsclient-$(cdsclient-version).tar.gz \
-                        cfitsio-$(cfitsio-version).tar.gz \
-                        cmake-$(cmake-version).tar.gz \
-                        eigen-$(eigen-version).tar.gz \
-                        expat-$(expat-version).tar.lz \
-                        fftw-$(fftw-version).tar.gz \
-                        flex-$(flex-version).tar.gz \
-                        freetype-$(freetype-version).tar.gz \
-                        gdb-$(gdb-version).tar.gz \
-                        ghostscript-$(ghostscript-version).tar.gz \
-                        gnuastro-$(gnuastro-version).tar.lz \
-                        gsl-$(gsl-version).tar.gz \
-                        hdf5-$(hdf5-version).tar.gz \
-                        healpix-$(healpix-version).tar.gz \
-                        help2man-$(help2man-version).tar.xz \
-                        imagemagick-$(imagemagick-version).tar.xz \
-                        imfit-$(imfit-version).tar.gz \
-                        install-tl-unx.tar.gz \
-                        jpegsrc.$(libjpeg-version).tar.gz \
-                        lapack-$(lapack-version).tar.gz \
-                        libgit2-$(libgit2-version).tar.gz \
-                        libnsl-$(libnsl-version).tar.gz \
-                        libpng-$(libpng-version).tar.xz \
-                        libtirpc-$(libtirpc-version).tar.bz2 \
-                        missfits-$(missfits-version).tar.gz \
-                        netpbm-$(netpbm-version).tar.gz \
-                        openblas-$(openblas-version).tar.gz \
-                        openmpi-$(openmpi-version).tar.gz \
-                        openssh-$(openssh-version).tar.gz \
-                        patch-$(patch-version).tar.gz \
-                        pixman-$(pixman-version).tar.gz \
-                        R-$(R-version).tar.gz \
-                        scamp-$(scamp-version).tar.lz \
-                        scons-$(scons-version).tar.gz \
-                        sextractor-$(sextractor-version).tar.lz \
-                        swarp-$(swarp-version).tar.gz \
-                        swig-$(swig-version).tar.gz \
-                        rpcsvc-proto-$(rpcsvc-proto-version).tar.xz \
-                        tides-$(tides-version).tar.gz \
-                        tiff-$(libtiff-version).tar.gz \
-                        valgrind-$(valgrind-version).tar.bz2 \
-                        wcslib-$(wcslib-version).tar.bz2 \
-                        xlsxio-$(xlsxio-version).tar.gz \
-                        yaml-$(yaml-version).tar.gz \
-                        zlib-$(zlib-version).tar.gz \
-                      , $(tdir)/$(t) )
-$(tarballs): $(tdir)/%: | $(lockdir)
-
-        # Remove the version numbers and suffix from the tarball name so we
-        # can search more easily only with the program name. This requires
-        # the first character of the version to be a digit: packages such
-        # as `foo' and `foo-3' will not be distinguished, but `foo' and
-        # `foo2' will be distinguished.
-	@n=$$(echo $* | sed -e's/-[0-9]/ /' -e's/\./ /g' \
-	              | awk '{print $$1}' )
-
-        # Set the top download link of the requested tarball.
-	mergenames=1
-	if   [ $$n = apachelog4cxx ]; then c=$(apachelog4cxx-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = apr         ]; then c=$(apr-checksum); w=https://www-us.apache.org/dist/apr
-	elif [ $$n = apr-util    ]; then c=$(apr-util-checksum); w=https://www-us.apache.org/dist/apr
-	elif [ $$n = astrometry  ]; then c=$(astrometrynet-checksum); w=http://astrometry.net/downloads
-	elif [ $$n = atlas       ]; then
-	  mergenames=0
-	  c=$(atlas-checksum)
-	  w=https://sourceforge.net/projects/math-atlas/files/Stable/$(atlas-version)/atlas$(atlas-version).tar.bz2/download
-	elif [ $$n = autoconf    ]; then c=$(autoconf-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = automake    ]; then c=$(automake-checksum); w=http://ftp.gnu.org/gnu/automake
-	elif [ $$n = bison       ]; then c=$(bison-checksum); w=http://ftp.gnu.org/gnu/bison
-	elif [ $$n = boost       ]; then
-	  mergenames=0
-	  c=$(boost-checksum)
-	  vstr=$$(echo $(boost-version) | sed -e's/\./_/g')
-	  w=https://dl.bintray.com/boostorg/release/$(boost-version)/source/boost_$$vstr.tar.gz
-	elif [ $$n = cairo       ]; then c=$(cairo-checksum); w=https://www.cairographics.org/releases
-	elif [ $$n = cdsclient   ]; then c=$(cdsclient-checksum); w=http://cdsarc.u-strasbg.fr/ftp/pub/sw
-	elif [ $$n = cfitsio     ]; then c=$(cfitsio-checksum); w=https://heasarc.gsfc.nasa.gov/FTP/software/fitsio/c
-	elif [ $$n = cmake       ]; then
-	  mergenames=0
-	  c=$(cmake-checksum)
-	  majv=$$(echo $(cmake-version) \
-	               | sed -e's/\./ /' \
-	               | awk '{printf("%d.%d", $$1, $$2)}')
-	  w=https://cmake.org/files/v$$majv/cmake-$(cmake-version).tar.gz
-	elif [ $$n = eigen       ]; then
-	  mergenames=0
-	  c=$(eigen-checksum);
-	  w=http://bitbucket.org/eigen/eigen/get/$(eigen-version).tar.gz
-	elif [ $$n = expat    ]; then
-	  mergenames=0
-	  c=$(expat-checksum)
-	  vstr=$$(echo $(expat-version) | sed -e's/\./_/g')
-	  w=https://github.com/libexpat/libexpat/releases/download/R_$$vstr/expat-$(expat-version).tar.lz
-	elif [ $$n = fftw        ]; then c=$(fftw-checksum); w=ftp://ftp.fftw.org/pub/fftw
-	elif [ $$n = flex        ]; then c=$(flex-checksum); w=https://github.com/westes/flex/files/981163
-	elif [ $$n = freetype    ]; then c=$(freetype-checksum); w=https://download.savannah.gnu.org/releases/freetype
-	elif [ $$n = gdb         ]; then c=$(gdb-checksum); w=http://ftp.gnu.org/gnu/gdb
-	elif [ $$n = ghostscript ]; then
-	  c=$(ghostscript-checksum)
-	  v=$$(echo $(ghostscript-version) | sed -e's/\.//')
-	  w=https://github.com/ArtifexSoftware/ghostpdl-downloads/releases/download/gs$$v
-	elif [ $$n = gnuastro    ]; then c=$(gnuastro-checksum); w=http://ftp.gnu.org/gnu/gnuastro
-	elif [ $$n = gsl         ]; then c=$(gsl-checksum); w=http://ftp.gnu.org/gnu/gsl
-	elif [ $$n = hdf5        ]; then
-	  mergenames=0
-	  c=$(hdf5-checksum)
-	  majorver=$$(echo $(hdf5-version) | sed -e 's/\./ /g' | awk '{printf("%d.%d", $$1, $$2)}')
-	  w=https://support.hdfgroup.org/ftp/HDF5/releases/hdf5-$$majorver/hdf5-$(hdf5-version)/src/$*
-	elif [ $$n = healpix     ]; then c=$(healpix-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = help2man    ]; then c=$(help2man-checksum); w=http://ftp.gnu.org/gnu/help2man
-	elif [ $$n = imagemagick ]; then c=$(imagemagick-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = imfit       ]; then
-	  mergenames=0
-	  c=$(imfit-checksum)
-	  w=http://www.mpe.mpg.de/~erwin/resources/imfit/imfit-$(imfit-version)-source.tar.gz
-	elif [ $$n = install-tl-unx ]; then c=NO-CHECK-SUM; w=http://mirror.ctan.org/systems/texlive/tlnet
-	elif [ $$n = jpegsrc     ]; then c=$(libjpeg-checksum); w=http://ijg.org/files
-	elif [ $$n = lapack      ]; then c=$(lapack-checksum); w=http://www.netlib.org/lapack
-	elif [ $$n = libnsl      ]; then c=$(libnsl-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = libpng      ]; then c=$(libpng-checksum); w=https://download.sourceforge.net/libpng
-	elif [ $$n = libgit2     ]; then
-	  mergenames=0
-	  c=$(libgit2-checksum)
-	  w=https://github.com/libgit2/libgit2/archive/v$(libgit2-version).tar.gz
-	elif [ $$n = libtirpc    ]; then c=$(libtirpc-checksum); w=https://downloads.sourceforge.net/libtirpc
-	elif [ $$n = missfits    ]; then c=$(missfits-checksum); w=https://www.astromatic.net/download/missfits
-	elif [ $$n = netpbm      ]; then c=$(netpbm-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = openblas    ]; then
-	  mergenames=0
-	  c=$(openblas-checksum)
-	  w=https://github.com/xianyi/OpenBLAS/archive/v$(openblas-version).tar.gz
-	elif [ $$n = openmpi     ]; then
-	  mergenames=0
-	  c=$(openmpi-checksum)
-	  majorver=$$(echo $(openmpi-version) | sed -e 's/\./ /g' | awk '{printf("%d.%d", $$1, $$2)}')
-	  w=https://download.open-mpi.org/release/open-mpi/v$$majorver/$*
-	elif [ $$n = openssh     ]; then c=$(openssh-checksum); w=https://artfiles.org/openbsd/OpenSSH/portable
-	elif [ $$n = patch       ]; then c=$(patch-checksum); w=http://ftp.gnu.org/gnu/patch
-	elif [ $$n = pixman      ]; then c=$(pixman-checksum); w=https://www.cairographics.org/releases
-	elif [ $$n = R           ]; then c=$(R-checksum);
-	  majver=$$(echo $(R-version) | sed -e's/\./ /g' | awk '{print $$1}')
-	  w=https://cran.r-project.org/src/base/R-$$majver
-	elif [ $$n = rpcsvc-proto ]; then c=$(rpcsvc-proto-checksum); w=https://github.com/thkukuk/rpcsvc-proto/releases/download/v$(rpcsvc-proto-version)
-	elif [ $$n = scamp       ]; then c=$(scamp-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = scons       ]; then
-	  mergenames=0
-	  c=$(scons-checksum)
-	  w=https://sourceforge.net/projects/scons/files/scons/$(scons-version)/scons-$(scons-version).tar.gz/download
-	elif [ $$n = sextractor  ]; then c=$(sextractor-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = swarp       ]; then c=$(swarp-checksum); w=https://www.astromatic.net/download/swarp
-	elif [ $$n = swig        ]; then c=$(swig-checksum); w=https://sourceforge.net/projects/swig/files/swig/swig-$(swig-version)
-	elif [ $$n = tides       ]; then c=$(tides-checksum); w=http://akhlaghi.org/maneage-software
-	elif [ $$n = tiff        ]; then c=$(libtiff-checksum); w=https://download.osgeo.org/libtiff
-	elif [ $$n = valgrind    ]; then c=$(valgrind-checksum); w=https://sourceware.org/pub/valgrind
-	elif [ $$n = wcslib      ]; then c=$(wcslib-checksum); w=ftp://ftp.atnf.csiro.au/pub/software/wcslib
-	elif [ $$n = xlsxio      ]; then
-	  mergenames=0
-	  c=$(xlsxio-checksum);
-	  w=https://github.com/brechtsanders/xlsxio/archive/$(xlsxio-version).tar.gz
-	elif [ $$n = yaml        ]; then c=$(yaml-checksum); w=pyyaml.org/download/libyaml
-	elif [ $$n = zlib        ]; then c=$(zlib-checksum); w=https://zlib.net
-	else
-	  echo; echo; echo;
-	  echo "'$$n' not recognized as a software tarball name to download."
-	  echo; echo; echo;
-	  exit 1
-	fi
-
-        # Download the requested tarball. Note that some packages may not
-        # follow our naming convention (where the package name is merged
-        # with its version number). In such cases, `w' will be the full
-        # address, not just the top directory address. But since we are
-        # storing all the tarballs in one directory, we want it to have the
-        # same naming convention, so we'll download it to a temporary name,
-        # then rename that.
-	rm -f "$@.unchecked"
-	if [ -f $(DEPENDENCIES-DIR)/$* ]; then
-	  cp $(DEPENDENCIES-DIR)/$* "$@.unchecked"
-	else
-	  if [ $$mergenames = 1 ]; then  tarballurl=$$w/"$*"
-	  else                           tarballurl=$$w
-	  fi
-
-          # Download using the script specially defined for this job.
-	  touch $(lockdir)/download
-	  downloader="wget --no-use-server-timestamps -O"
-	  $(downloadwrapper) "$$downloader" $(lockdir)/download \
-	                     $$tarballurl "$@.unchecked" "$(backupservers)"
-	fi
-
-        # Make sure this is the expected tarball. Note that we now have a
-        # controlled `sha512sum' build (as part of GNU Coreutils). So we
-        # don't need to check its existance like `basic.mk'. But for LaTeX,
-        # we need to ignore a checksum (it downloads the binaries).
-	if [ x"$$c" == x"NO-CHECK-SUM" ]; then
-	  mv "$@.unchecked" "$@"
-	else
-	  checksum=$$(sha512sum "$@.unchecked" | awk '{print $$1}')
-	  if [ x"$$checksum" = x"$$c" ]; then
-	    mv "$@.unchecked" "$@"
-	  else
-	    echo "ERROR: Non-matching checksum for '$*'."
-	    echo "Checksum should be: $$c"
-	    echo "Checksum is:        $$checksum"
-	    exit 1
-	  fi
-	fi
-
-
-
-
-
 
 
 
@@ -409,39 +233,50 @@ $(tarballs): $(tdir)/%: | $(lockdir)
 # build it because it will complain about the version of libtool, so until
 # the version 0.11.0 of log4cxx, we'll have to run `autogen.sh' on the
 # unpacked source also.
-$(ibidir)/apachelog4cxx: $(ibidir)/automake \
-                         $(tdir)/apachelog4cxx-$(apachelog4cxx-version).tar.lz
-
+$(ibidir)/apachelog4cxx-$(apachelog4cxx-version): \
+                        $(ibidir)/expat-$(expat-version) \
+                        $(ibidir)/apr-util-$(apr-util-version) \
+                        $(ibidir)/automake-$(automake-version)
+	tarball=apachelog4cxx-$(apachelog4cxx-version).tar.lz
+	$(call import-source, $(apachelog4cxx-url), $(apachelog4cxx-checksum))
 	pdir=apachelog4cxx-$(apachelog4cxx-version)
 	rm -rf $(ddir)/$$pdir
 	topdir=$(pwd)
 	cd $(ddir)
-	tar xf $(word 1,$(filter $(tdir)/%,$^))
+	tar xf $(tdir)/$$tarball
 	cd $$pdir
-	./autogen.sh \
-	&& ./configure SHELL=$(ibdir)/bash --prefix=$(idir) \
-	&& make -j$(numthreads) SHELL=$(ibdir)/bash \
-	&& make install \
-	&& cd .. \
-	&& rm -rf $$pdir \
-	&& cd $$topdir \
-	&& echo "Apache log4cxx $(apachelog4cxx-version)" > $@
-
-$(ibidir)/apr: $(tdir)/apr-$(apr-version).tar.gz
-	$(call gbuild, apr-$(apr-version), ,--disable-static) \
-	&& echo "Apache Portable Runtime $(apr-version)" > $@
-
-$(ibidir)/apr-util: $(ibidir)/apr \
-                    $(tdir)/apr-util-$(apr-util-version).tar.gz
+	./autogen.sh
+	./configure SHELL=$(ibdir)/bash --prefix=$(idir)
+	make -j$(numthreads) SHELL=$(ibdir)/bash
+	make install
+	cd ..
+	rm -rf $$pdir
+	cd $$topdir
+	echo "Apache log4cxx $(apachelog4cxx-version)" > $@
+
+$(ibidir)/apr-$(apr-version):
+	tarball=apr-$(apr-version).tar.gz
+	$(call import-source, $(apr-url), $(apr-checksum))
+	$(call gbuild, apr-$(apr-version), ,--disable-static)
+	echo "Apache Portable Runtime $(apr-version)" > $@
+
+$(ibidir)/apr-util-$(apr-util-version): $(ibidir)/apr-$(apr-version)
+	tarball=apr-util-$(apr-util-version).tar.gz
+	$(call import-source, $(apr-util-url), $(apr-util-checksum))
 	$(call gbuild, apr-util-$(apr-util-version), , \
 	               --disable-static \
 	               --with-apr=$(idir) \
 	               --with-openssl=$(idir) \
-	               --with-crypto ) \
-	&& echo "Apache Portable Runtime Utility $(apr-util-version)" > $@
+	               --with-crypto )
+	echo "Apache Portable Runtime Utility $(apr-util-version)" > $@
+
+$(ibidir)/atlas-$(atlas-version):
 
-$(ibidir)/atlas: $(tdir)/atlas-$(atlas-version).tar.bz2 \
-                 $(tdir)/lapack-$(lapack-version).tar.gz
+	tarball=lapack-$(lapack-version).tar.gz
+	$(call import-source, $(lapack-url), $(lapack-checksum))
+
+	tarball=atlas-$(atlas-version).tar.bz2
+	$(call import-source, $(atlas-url), $(atlas-checksum))
 
         # Get the operating system specific features (how to get
         # CPU frequency and the library suffixes). To make the steps
@@ -470,39 +305,46 @@ $(ibidir)/atlas: $(tdir)/atlas-$(atlas-version).tar.bz2 \
         # See if the shared libraries should be build for a single CPU
         # thread or multiple threads.
 	N=$$(nproc)
-	srcdir=$$(pwd)/reproduce/src/make
+	srcdir=$$(pwd)/reproduce/software/make
 	if [ $$N = 1 ]; then
-	  sharedmk=$$srcdir/dependencies-atlas-single.mk
+	  sharedmk=$$srcdir/atlas-single.mk
 	else
-	  sharedmk=$$srcdir/dependencies-atlas-multiple.mk
+	  sharedmk=$$srcdir/atlas-multiple.mk
 	fi
 
         # The linking step here doesn't recognize the `-Wl' in the
         # `rpath_command'.
 	export LDFLAGS=-L$(ildir)
-	cd $(ddir) \
-	&& tar xf $(tdir)/atlas-$(atlas-version).tar.bz2 \
-	&& cd ATLAS \
-	&& rm -rf build \
-	&& mkdir build \
-	&& cd build \
-	&& ../configure -b 64 -D c -DPentiumCPS=$$core \
+	cd $(ddir)
+	tar xf $(tdir)/atlas-$(atlas-version).tar.bz2
+	cd ATLAS
+	rm -rf build
+	mkdir build
+	cd build
+	../configure -b 64 -D c -DPentiumCPS=$$core \
 	             --with-netlib-lapack-tarfile=$(tdir)/lapack-$(lapack-version).tar.gz \
 	             --cripple-atlas-performance \
 	             -Fa alg -fPIC --shared $$clangflag \
-	             --prefix=$(idir) \
-	&& make \
-	&& if [ "x$(on_mac_os)" != xyes ]; then \
-	     cd lib && make -f $$sharedmk && cd .. \
-	     && for l in lib/*.$$s*; do \
-	          patchelf --set-rpath $(ildir) $$l; done \
-	     && cp -d lib/*.$$s* $(ildir) \
-	     && ln -fs $(ildir)/libblas.$$s  $(ildir)/libblas.$$m \
-	     && ln -fs $(ildir)/libf77blas.$$s $(ildir)/libf77blas.$$m \
-	     && ln -fs $(ildir)/liblapack.$$f  $(ildir)/liblapack.$$s \
-	     && ln -fs $(ildir)/liblapack.$$f  $(ildir)/liblapack.$$m; \
-	   fi \
-	&& make install
+	             --prefix=$(idir)
+
+        # Static build.
+	make
+
+        # Currently the shared libraries have problems on macOS.
+	if [ "x$(on_mac_os)" != xyes ]; then
+	     cd lib
+	     make -f $$sharedmk
+	     cd ..
+	     for l in lib/*.$$s*; do patchelf --set-rpath $(ildir) $$l; done
+	     cp -d lib/*.$$s* $(ildir)
+	     ln -fs $(ildir)/libblas.$$s  $(ildir)/libblas.$$m
+	     ln -fs $(ildir)/libf77blas.$$s $(ildir)/libf77blas.$$m
+	     ln -fs $(ildir)/liblapack.$$f  $(ildir)/liblapack.$$s
+	     ln -fs $(ildir)/liblapack.$$f  $(ildir)/liblapack.$$m
+	   fi
+
+        # Install the libraries.
+	make install
 
         # We need to check the existance of `libptlapack.a', but we can't
         # do this in the `&&' steps above (it will conflict). So we'll do
@@ -521,31 +363,37 @@ $(ibidir)/atlas: $(tdir)/atlas-$(atlas-version).tar.bz2 \
 	fi
 
 # Boost doesn't use the standard GNU Build System.
-$(ibidir)/boost: $(ibidir)/openmpi \
-                 $(ibidir)/python \
-                 $(tdir)/boost-$(boost-version).tar.gz
-	vstr=$$(echo $(boost-version) | sed -e's/\./_/g')
-	rm -rf $(ddir)/boost_$$vstr
-	topdir=$(pwd); cd $(ddir);
-	tar xf $(word 1,$(filter $(tdir)/%,$^)) \
-	&& cd boost_$$vstr \
-	&& ./bootstrap.sh --prefix=$(idir) --with-libraries=all \
-	                  --with-python=python3 \
-	&& echo "using mpi ;" > project-config.jam \
-	&& ./b2 stage threading=multi link=shared --prefix=$(idir) -j$(numthreads) \
-	&& ./b2 install threading=multi link=shared --prefix=$(idir) -j$(numthreads) \
-	&& cd $$topdir \
-	&& rm -rf $(ddir)/boost_$$vstr \
-	&& echo "Boost $(boost-version)" > $@
-
-$(ibidir)/cfitsio: $(ibidir)/curl \
-                   $(tdir)/cfitsio-$(cfitsio-version).tar.gz
+$(ibidir)/boost-$(boost-version): \
+                $(ibidir)/python-$(python-version) \
+                $(ibidir)/openmpi-$(openmpi-version)
+	tarball=boost-$(boost-version).tar.lz
+	$(call import-source, $(boost-url), $(boost-checksum))
+	unpackdir=boost-$(boost-version)
+	rm -rf $(ddir)/$$unpackdir
+	topdir=$(pwd)
+	cd $(ddir)
+	tar xf $(tdir)/$$tarball
+	cd $$unpackdir
+	./bootstrap.sh --prefix=$(idir) --with-libraries=all \
+	               --with-python=python3
+	echo "using mpi ;" > project-config.jam
+	./b2 stage threading=multi link=shared --prefix=$(idir) -j$(numthreads)
+	./b2 install threading=multi link=shared --prefix=$(idir) -j$(numthreads)
+	cd $$topdir
+	rm -rf $(ddir)/$$unpackdir
+	echo "Boost $(boost-version)" > $@
+
+$(ibidir)/cfitsio-$(cfitsio-version):
+
+        # Download the tarball
+	tarball=cfitsio-$(cfitsio-version).tar.gz
+	$(call import-source, $(cfitsio-url), $(cfitsio-checksum))
 
         # CFITSIO hard-codes '@rpath' inside the shared library on
         # Mac systems. So we need to change it to our library
         # installation path. It doesn't affect GNU/Linux, so we'll
         # just do it in any case to keep things clean.
-	topdir=$(pwd); cd $(ddir); tar xf $(word 1,$(filter $(tdir)/%,$^))
+	topdir=$(pwd); cd $(ddir); tar xf $(tdir)/$$tarball
 	customtar=cfitsio-$(cfitsio-version)-custom.tar.gz
 	cd cfitsio-$(cfitsio-version)
 	sed configure -e's|@rpath|$(ildir)|g' > configure_tmp
@@ -558,68 +406,82 @@ $(ibidir)/cfitsio: $(ibidir)/curl \
         # Continue the standard build on the customized tarball. Note that
         # with the installation of CFITSIO, `fpack' and `funpack' are not
         # installed by default. Because of that, they are added explicity.
-	export gbuild_tar=$$customtar
+	export gbuild_tar=$(ddir)/$$customtar
 	$(call gbuild, cfitsio-$(cfitsio-version), , \
 	               --enable-sse2 --enable-reentrant \
-	               --with-bzip2=$(idir), , make shared fpack funpack) \
-	&& rm $$customtar \
-	&& echo "CFITSIO $(cfitsio-version)" > $@
-
-$(ibidir)/cairo: $(ibidir)/freetype \
-                 $(ibidir)/libpng \
-                 $(ibidir)/pixman \
-                 $(tdir)/cairo-$(cairo-version).tar.xz
+	               --with-bzip2=$(idir), , make shared fpack funpack)
+	rm $$customtar
+	echo "CFITSIO $(cfitsio-version)" > $@
+
+$(ibidir)/cairo-$(cairo-version): \
+                $(ibidir)/pixman-$(pixman-version) \
+                $(ibidir)/libpng-$(libpng-version) \
+                $(ibidir)/freetype-$(freetype-version)
+	tarball=cairo-$(cairo-version).tar.xz
+	$(call import-source, $(cairo-url), $(cairo-checksum))
 	$(call gbuild, cairo-$(cairo-version), static, \
-	               --with-x=no, -j$(numthreads) V=1) \
-	&& echo "Cairo $(cairo-version)" > $@
+	               --with-x=yes, -j$(numthreads) V=1)
+	echo "Cairo $(cairo-version)" > $@
 
 # Eigen is just headers! So it doesn't need to be compiled. Once unpacked
 # it has a checksum after `eigen-eigen', so we'll just use a `*' to choose
 # the unpacked directory.
-$(ibidir)/eigen: $(tdir)/eigen-$(eigen-version).tar.gz
+$(ibidir)/eigen-$(eigen-version):
+	tarball=eigen-$(eigen-version).tar.gz
+	$(call import-source, $(eigen-url), $(eigen-checksum))
 	rm -rf $(ddir)/eigen-eigen-*
-	topdir=$(pwd); cd $(ddir); tar xf $(word 1,$(filter $(tdir)/%,$^))
+	topdir=$(pwd); cd $(ddir); tar xf $(tdir)/$$tarball
 	cd eigen-eigen-*
-	cp -r Eigen $(iidir)/eigen3 \
-	&& cd $$topdir \
-	&& rm -rf $(ddir)/eigen-eigen-* \
-	&& echo "Eigen $(eigen-version)" > $@
+	cp -r Eigen $(iidir)/eigen3
+	cd $$topdir
+	rm -rf $(ddir)/eigen-eigen-*
+	echo "Eigen $(eigen-version)" > $@
+
+$(ibidir)/expat-$(expat-version):
+	tarball=expat-$(expat-version).tar.lz
+	$(call import-source, $(expat-url), $(expat-checksum))
+	$(call gbuild, expat-$(expat-version), static)
+	echo "Expat $(expat-version)" > $@
 
-$(ibidir)/expat: $(tdir)/expat-$(expat-version).tar.lz
-	$(call gbuild, expat-$(expat-version), static) \
-	&& echo "Expat $(expat-version)" > $@
+$(ibidir)/fftw-$(fftw-version):
+        # Prepare the source tarball.
+	tarball=fftw-$(fftw-version).tar.gz
+	$(call import-source, $(fftw-url), $(fftw-checksum))
 
-$(ibidir)/fftw: $(tdir)/fftw-$(fftw-version).tar.gz
         # FFTW's single and double precission libraries must be built
         # independently: for the the single-precision library, we need to
         # add the `--enable-float' option. We will build this first, then
         # the default double-precision library.
 	confop="--enable-shared --enable-threads --enable-avx --enable-sse2"
 	$(call gbuild, fftw-$(fftw-version), static, \
-	               $$confop --enable-float) \
-	&& $(call gbuild, fftw-$(fftw-version), static, \
-	               $$confop) \
-	&& cp $(dtexdir)/fftw.tex $(ictdir)/ \
-	&& echo "FFTW $(fftw-version) \citep{fftw}" > $@
-
-# Freetype is necessary to install matplotlib
-$(ibidir)/freetype: $(ibidir)/libpng \
-                    $(tdir)/freetype-$(freetype-version).tar.gz
-	$(call gbuild, freetype-$(freetype-version), static) \
-	&& echo "FreeType $(freetype-version)" > $@
-
-$(ibidir)/gsl: $(tdir)/gsl-$(gsl-version).tar.gz
-	$(call gbuild, gsl-$(gsl-version), static) \
-	&& echo "GNU Scientific Library $(gsl-version)" > $@
-
-$(ibidir)/hdf5: $(ibidir)/openmpi \
-                $(tdir)/hdf5-$(hdf5-version).tar.gz
-	export CC=mpicc; \
-	export FC=mpif90; \
+	               $$confop --enable-float)
+	$(call gbuild, fftw-$(fftw-version), static, \
+	               $$confop)
+	cp $(dtexdir)/fftw.tex $(ictdir)/
+	echo "FFTW $(fftw-version) \citep{fftw}" > $@
+
+$(ibidir)/freetype-$(freetype-version): $(ibidir)/libpng-$(libpng-version)
+	tarball=freetype-$(freetype-version).tar.gz
+	$(call import-source, $(freetype-url), $(freetype-checksum))
+	$(call gbuild, freetype-$(freetype-version), static)
+	echo "FreeType $(freetype-version)" > $@
+
+$(ibidir)/gsl-$(gsl-version):
+	tarball=gsl-$(gsl-version).tar.gz
+	$(call import-source, $(gsl-url), $(gsl-checksum))
+	$(call gbuild, gsl-$(gsl-version), static)
+	echo "GNU Scientific Library $(gsl-version)" > $@
+
+$(ibidir)/hdf5-$(hdf5-version): $(ibidir)/openmpi-$(openmpi-version)
+	export CC=mpicc
+	export FC=mpif90
+	tarball=hdf5-$(hdf5-version).tar.gz
+	$(call import-source, $(hdf5-url), $(hdf5-checksum))
 	$(call gbuild, hdf5-$(hdf5-version), static, \
 	               --enable-parallel \
-	               --enable-fortran, -j$(numthreads) V=1) \
-	&& echo "HDF5 library $(hdf5-version)" > $@
+	               --enable-fortran, \
+	               -j$(numthreads) V=1)
+	echo "HDF5 library $(hdf5-version)" > $@
 
 # HEALPix includes the source of its C, C++, Python (and several other
 # languages) libraries within one tarball. We will include the Python
@@ -634,13 +496,15 @@ $(ibidir)/hdf5: $(ibidir)/openmpi \
 ifeq ($(strip $(top-level-python)),)
 healpix-python-dep =
 else
-healpix-python-dep = $(ipydir)/matplotlib $(ipydir)/astropy
+healpix-python-dep = $(ipydir)/matplotlib-$(matplotlib-version) \
+                     $(ipydir)/astropy-$(astropy-version)
 endif
-$(ibidir)/healpix: $(ibidir)/cfitsio \
-                   $(ibidir)/autoconf \
-                   $(ibidir)/automake \
-                   $(healpix-python-dep) \
-                   $(tdir)/healpix-$(healpix-version).tar.gz
+$(ibidir)/healpix-$(healpix-version): $(healpix-python-dep) \
+                  $(ibidir)/cfitsio-$(cfitsio-version) \
+                  $(ibidir)/autoconf-$(autoconf-version) \
+                  $(ibidir)/automake-$(automake-version)
+	tarball=healpix-$(healpix-version).tar.gz
+	$(call import-source, $(healpix-url), $(healpix-checksum))
 	if [ x"$(healpix-python-dep)" = x ]; then
 	   pycommand1="echo no-healpy-because-no-other-python"
 	   pycommand2="echo no-healpy-because-no-other-python"
@@ -650,130 +514,194 @@ $(ibidir)/healpix: $(ibidir)/cfitsio \
 	fi
 	rm -rf $(ddir)/Healpix_$(healpix-version)
 	topdir=$(pwd); cd $(ddir);
-	tar xf $(word 1,$(filter $(tdir)/%,$^))
-	&& cd Healpix_$(healpix-version)/src/C/autotools/ \
-	&& autoreconf --install \
-	&& ./configure --prefix=$(idir) \
-	&& make V=1 -j$(numthreads) SHELL=$(ibdir)/bash \
-	&& make install \
-	&& cd ../../cxx/autotools/ \
-	&& autoreconf --install \
-	&& ./configure --prefix=$(idir) \
-	&& make V=1 -j$(numthreads) SHELL=$(ibdir)/bash \
-	&& make install \
-	&& cd ../../healpy \
-	&& $$pycommand1 \
-	&& $$pycommand2 \
-	&& cd $$topdir \
-	&& rm -rf $(ddir)/Healpix_$(healpix-version) \
-	&& cp $(dtexdir)/healpix.tex $(ictdir)/ \
-	&& echo "HEALPix $(healpix-version) \citep{healpix}" > $@
-
-$(ibidir)/libjpeg: $(tdir)/jpegsrc.$(libjpeg-version).tar.gz
-	$(call gbuild, jpeg-9b, static,,V=1) \
-	&& echo "Libjpeg $(libjpeg-version)" > $@
-
-$(ibidir)/libnsl: $(ibidir)/libtirpc \
-                  $(ibidir)/rpcsvc-proto \
-                  $(tdir)/libnsl-$(libnsl-version).tar.gz
+	tar xf $(tdir)/$$tarball
+	cd Healpix_$(healpix-version)/src/C/autotools/
+	autoreconf --install
+	./configure --prefix=$(idir)
+	make V=1 -j$(numthreads) SHELL=$(ibdir)/bash
+	make install
+	cd ../../cxx/autotools/
+	autoreconf --install
+	./configure --prefix=$(idir)
+	make V=1 -j$(numthreads) SHELL=$(ibdir)/bash
+	make install
+	cd ../../healpy
+	$$pycommand1
+	$$pycommand2
+	cd $$topdir
+	rm -rf $(ddir)/Healpix_$(healpix-version)
+	cp $(dtexdir)/healpix.tex $(ictdir)/
+	echo "HEALPix $(healpix-version) \citep{healpix}" > $@
+
+$(ibidir)/libjpeg-$(libjpeg-version):
+	tarball=jpegsrc.$(libjpeg-version).tar.gz
+	$(call import-source, $(libjpeg-url), $(libjpeg-checksum))
+	$(call gbuild, jpeg-9b, static,,V=1)
+	echo "Libjpeg $(libjpeg-version)" > $@
+
+$(ibidir)/libnsl-$(libnsl-version): \
+                 $(ibidir)/libtirpc-$(libtirpc-version) \
+                 $(ibidir)/rpcsvc-proto-$(rpcsvc-proto-version)
+	tarball=libnsl-$(libnsl-version).tar.gz
+	$(call import-source, $(libnsl-url), $(libnsl-checksum))
 	$(call gbuild, libnsl-$(libnsl-version), static, \
-	               --sysconfdir=$(idir)/etc) \
-	&& echo "Libnsl $(libnsl-version)" > $@
+	               --sysconfdir=$(idir)/etc)
+	echo "Libnsl $(libnsl-version)" > $@
+
+$(ibidir)/libpaper-$(libpaper-version): \
+                   $(ibidir)/automake-$(automake-version)
 
-$(ibidir)/libpng: $(tdir)/libpng-$(libpng-version).tar.xz
-	$(call gbuild, libpng-$(libpng-version), static) \
-	&& echo "Libpng $(libpng-version)" > $@
+        # Download the tarball.
+	tarball=libpaper-$(libpaper-version).tar.gz
+	$(call import-source, $(libpaper-url), $(libpaper-checksum))
 
-$(ibidir)/libtiff: $(ibidir)/libjpeg \
-                   $(tdir)/tiff-$(libtiff-version).tar.gz
+        # Unpack, build the configure system, build and install.
+	cd $(ddir)
+	tar -xf $(tdir)/$$tarball
+	unpackdir=libpaper-$(libpaper-version)
+	cd $$unpackdir
+	autoreconf -fi
+	./configure --prefix=$(idir) --sysconfdir=$(idir)/etc \
+	            --disable-static
+	make
+	make install
+	cd ..
+	rm -rf $$unpackdir
+
+        # Post-processing: according to Linux From Scratch, libpaper
+        # expects that packages will install files into this directory and
+        # 'paperconfig' is a script which will invoke 'run-parts' if
+        # '/etc/libpaper.d' exists
+	mkdir -vp $(idir)/etc/libpaper.d
+	sed -e's|MANEAGESHELL|$(SHELL)|' $(shsrcdir)/run-parts.in \
+	    > $(ibdir)/run-parts
+	chmod +x $(ibdir)/run-parts
+	echo "Libpaper $(libpaper-version)" > $@
+
+$(ibidir)/libpng-$(libpng-version):
+	tarball=libpng-$(libpng-version).tar.xz
+	$(call import-source, $(libpng-url), $(libpng-checksum))
+	$(call gbuild, libpng-$(libpng-version), static)
+	echo "Libpng $(libpng-version)" > $@
+
+$(ibidir)/libtiff-$(libtiff-version): $(ibidir)/libjpeg-$(libjpeg-version)
+	tarball=tiff-$(libtiff-version).tar.gz
+	$(call import-source, $(libtiff-url), $(libtiff-checksum))
 	$(call gbuild, tiff-$(libtiff-version), static, \
 	               --disable-jbig \
 	               --disable-webp \
-	               --disable-zstd) \
-	&& echo "Libtiff $(libtiff-version)" > $@
+	               --disable-zstd)
+	echo "Libtiff $(libtiff-version)" > $@
 
-$(ibidir)/libtirpc: $(tdir)/libtirpc-$(libtirpc-version).tar.bz2
+$(ibidir)/libtirpc-$(libtirpc-version):
+	tarball=libtirpc-$(libtirpc-version).tar.bz2
+	$(call import-source, $(libtirpc-url), $(libtirpc-checksum))
 	$(call gbuild, libtirpc-$(libtirpc-version), static, \
-	               --disable-gssapi, V=1) \
+	               --disable-gssapi, V=1)
 	echo "libtirpc $(libtirpc-version)" > $@
 
-$(ibidir)/openblas: $(tdir)/openblas-$(openblas-version).tar.gz
-	if [ x$(on_mac_os) = xyes ]; then \
-	  export CC=clang; \
-	fi; \
-	cd $(ddir) \
-	&& tar xf $(word 1,$(filter $(tdir)/%,$^)) \
-	&& cd OpenBLAS-$(openblas-version) \
-	&& make \
-	&& make PREFIX=$(idir) install \
-	&& cd .. \
-	&& rm -rf OpenBLAS-$(openblas-version) \
-	&& echo "OpenBLAS $(openblas-version)" > $@
-
-$(ibidir)/openmpi: $(tdir)/openmpi-$(openmpi-version).tar.gz
+$(ibidir)/openblas-$(openblas-version):
+	tarball=OpenBLAS-$(openblas-version).tar.gz
+	$(call import-source, $(openblas-url), $(openblas-checksum))
+	if [ x$(on_mac_os) = xyes ]; then export CC=clang; fi
+	cd $(ddir)
+	tar xf $(tdir)/$$tarball
+	cd OpenBLAS-$(openblas-version)
+	make -j$(numthreads)
+	make PREFIX=$(idir) install
+	cd ..
+	rm -rf OpenBLAS-$(openblas-version)
+	echo "OpenBLAS $(openblas-version)" > $@
+
+$(ibidir)/openmpi-$(openmpi-version):
+	tarball=openmpi-$(openmpi-version).tar.gz
+	$(call import-source, $(openmpi-url), $(openmpi-checksum))
 	$(call gbuild, openmpi-$(openmpi-version), static, , \
-	               -j$(numthreads) V=1) \
-	&& echo "Open MPI $(openmpi-version)" > $@
+	               -j$(numthreads) V=1)
+	echo "Open MPI $(openmpi-version)" > $@
 
 # IMPORTANT NOTE: The build instructions for OpenSSH are defined here, but
 # it is best that it not be prerequisite of any program and thus not built
 # within the project because of all the security issues it may cause. Only
 # enable/build it in a project with caution, and if there is no other
 # solution (for example to disable SSH in a program that may ask for it.
-$(ibidir)/openssh: $(tdir)/openssh-$(openssh-version).tar.gz
+$(ibidir)/openssh-$(openssh-version):
+	tarball=openssh-$(openssh-version).tar.gz
+	$(call import-source, $(openssh-url), $(openssh-checksum))
 	$(call gbuild, openssh-$(openssh-version), static, \
 	               --with-privsep-path=$(ibdir)/.ssh_privsep \
 	               --with-privsep-user=nobody \
 	               --with-md5-passwords \
 	               --with-ssl-engine \
-	               , -j$(numthreads) V=1) \
-	&& echo "OpenSSH $(openssh-version)" > $@
+	               , -j$(numthreads) V=1)
+	echo "OpenSSH $(openssh-version)" > $@
 
-$(ibidir)/pixman: $(tdir)/pixman-$(pixman-version).tar.gz
+$(ibidir)/pixman-$(pixman-version):
+	tarball=pixman-$(pixman-version).tar.gz
+	$(call import-source, $(pixman-url), $(pixman-checksum))
 	$(call gbuild, pixman-$(pixman-version), static, , \
-	                   -j$(numthreads) V=1) \
-	&& echo "Pixman $(pixman-version)" > $@
+	               -j$(numthreads) V=1)
+	echo "Pixman $(pixman-version)" > $@
 
-$(ibidir)/rpcsvc-proto: $(tdir)/rpcsvc-proto-$(rpcsvc-proto-version).tar.xz
-	$(call gbuild, rpcsvc-proto-$(rpcsvc-proto-version), static) \
-	&& echo "rpcsvc $(rpcsvc-proto-version)" > $@
+$(ibidir)/rpcsvc-proto-$(rpcsvc-proto-version):
+        # 'libintl' is installed as part of GNU Gettext in
+        # 'basic.mk'. rpcsvc-proto needs to link with it on macOS.
+	if [ x$(on_mac_os) = xyes ]; then
+	  export CC=clang
+	  export CXX=clang++
+	  export LDFLAGS="-lintl $$LDFLAGS"
+	fi
 
-$(ibidir)/tides: $(tdir)/tides-$(tides-version).tar.gz
+        # Download the tarball and build rpcsvc-proto.
+	tarball=rpcsvc-proto-$(rpcsvc-proto-version).tar.xz
+	$(call import-source, $(rpcsvc-proto-url), $(rpcsvc-proto-checksum))
+	$(call gbuild, rpcsvc-proto-$(rpcsvc-proto-version), static)
+	echo "rpcsvc $(rpcsvc-proto-version)" > $@
+
+$(ibidir)/tides-$(tides-version):
+	tarball=tides-$(tides-version).tar.gz
+	$(call import-source, $(tides-url), $(tides-checksum))
 	$(call gbuild, tides-$(tides-version), static,\
-	               --with-gmp=$(idir) --with-mpfr=$(idir)) \
-	&& cp $(dtexdir)/tides.tex $(ictdir)/ \
-	&& echo "TIDES $(tides-version) \citep{tides}" > $@
-
-$(ibidir)/valgrind: $(ibidir)/patch \
-                    $(ibidir)/autoconf \
-                    $(ibidir)/automake \
-                    $(tdir)/valgrind-$(valgrind-version).tar.bz2
+	               --with-gmp=$(idir) --with-mpfr=$(idir))
+	cp $(dtexdir)/tides.tex $(ictdir)/
+	echo "TIDES $(tides-version) \citep{tides}" > $@
+
+$(ibidir)/valgrind-$(valgrind-version): \
+                   $(ibidir)/patch-$(patch-version) \
+                   $(ibidir)/autoconf-$(autoconf-version) \
+                   $(ibidir)/automake-$(automake-version)
+        # Import the tarball
+	tarball=valgrind-$(valgrind-version).tar.bz2
+	$(call import-source, $(valgrind-url), $(valgrind-checksum))
+
         # For valgrind-3.15.0, see
         # https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=946329 for a
         # report on an MPI-related compile bug and the two patches
         # below. These two patches and `automake` should allow valgrind to
         # compile with gcc-9.2.0.
-	cd $(ddir) \
-	&& tar -x -f $(word 1,$(filter $(tdir)/%,$^)) \
-	&& valgrinddir=valgrind-$(valgrind-version) \
-	&& cd $${valgrinddir} \
-	&& printf "valgrindir=$${valgrinddir} ; pwd = %s .\n" $$($(ibdir)/pwd) \
-	&& if [ "x$(valgrind-version)" = "x3.15.0" ]; then \
-	     patch --verbose -p1 < $(patchdir)/valgrind-3.15.0-mpi-fix1.patch; \
-	     patch --verbose -p1 < $(patchdir)/valgrind-3.15.0-mpi-fix2.patch; \
-	   fi \
-	&& autoreconf \
-	&& ./configure --prefix=$(idir) \
-	&& make -j$(numthreads) \
-	&& if ! make check -j$(numthreads); then \
-	     echo; echo "Valgrind's 'make check' failed!"; echo; \
-	   fi \
-	&& make install \
-	&& echo "Valgrind $(valgrind-version)" > $@
+	cd $(ddir)
+	tar -xf $(tdir)/$$tarball
+	valgrinddir=valgrind-$(valgrind-version)
+	cd $${valgrinddir}
+	printf "valgrindir=$${valgrinddir} ; pwd = %s .\n" $$($(ibdir)/pwd)
+	if [ "x$(valgrind-version)" = "x3.15.0" ]; then
+	  patch --verbose -p1 < $(patchdir)/valgrind-3.15.0-mpi-fix1.patch
+	  patch --verbose -p1 < $(patchdir)/valgrind-3.15.0-mpi-fix2.patch
+	fi
+	autoreconf
+	./configure --prefix=$(idir)
+	make -j$(numthreads)
+	if ! make check -j$(numthreads); then
+	  echo; echo "Valgrind's 'make check' failed!"; echo
+	fi
+	make install
+	echo "Valgrind $(valgrind-version)" > $@
 
-$(ibidir)/yaml: $(tdir)/yaml-$(yaml-version).tar.gz
-	$(call gbuild, yaml-$(yaml-version), static) \
-	&& echo "LibYAML $(yaml-version)" > $@
+$(ibidir)/yaml-$(yaml-version):
+	tarball=yaml-$(yaml-version).tar.gz
+	$(call import-source, $(yaml-url), $(yaml-checksum))
+	$(call gbuild, yaml-$(yaml-version), static)
+	echo "LibYAML $(yaml-version)" > $@
 
 
 
@@ -800,20 +728,23 @@ $(ibidir)/yaml: $(tdir)/yaml-$(yaml-version).tar.gz
 # functions! But apparently `libgit2' has its own implementation of libiconv
 # that it uses if it can't find libiconv on macOS. So, to fix this problem
 # it is necessary to use the option `-DUSE_ICONV=OFF` in the configure step.
-$(ibidir)/libgit2: $(ibidir)/curl \
-                   $(ibidir)/cmake \
-                   $(tdir)/libgit2-$(libgit2-version).tar.gz
+$(ibidir)/libgit2-$(libgit2-version): $(ibidir)/cmake-$(cmake-version)
+	tarball=libgit2-$(libgit2-version).tar.gz
+	$(call import-source, $(libgit2-url), $(libgit2-checksum))
 	$(call cbuild, libgit2-$(libgit2-version), static, \
 	              -DUSE_SSH=OFF -DBUILD_CLAR=OFF \
-	              -DTHREADSAFE=ON -DUSE_ICONV=OFF ) \
-	&& if [ x$(on_mac_os) = xyes ]; then \
-	     install_name_tool -id $(ildir)/libgit2.28.dylib \
-	                           $(ildir)/libgit2.28.dylib; \
-	   fi \
-	&& echo "Libgit2 $(libgit2-version)" > $@
-
-$(ibidir)/wcslib: $(ibidir)/cfitsio \
-                  $(tdir)/wcslib-$(wcslib-version).tar.bz2
+	              -DTHREADSAFE=ON -DUSE_ICONV=OFF )
+	if [ x$(on_mac_os) = xyes ]; then
+	  install_name_tool -id $(ildir)/libgit2.28.dylib \
+	                        $(ildir)/libgit2.28.dylib
+	fi
+	echo "Libgit2 $(libgit2-version)" > $@
+
+$(ibidir)/wcslib-$(wcslib-version): $(ibidir)/cfitsio-$(cfitsio-version)
+        # Import the tarball.
+	tarball=wcslib-$(wcslib-version).tar.bz2
+	$(call import-source, $(wcslib-url), $(wcslib-checksum))
+
         # If Fortran isn't present, don't build WCSLIB with it.
 	if type gfortran &> /dev/null; then fortranopt="";
 	else fortranopt="--disable-fortran"
@@ -824,12 +755,12 @@ $(ibidir)/wcslib: $(ibidir)/cfitsio \
 	               LIBS="-pthread -lcurl -lm" \
                        --with-cfitsiolib=$(ildir) \
                        --with-cfitsioinc=$(idir)/include \
-                       --without-pgplot $$fortranopt) \
-	&& if [ x$(on_mac_os) = xyes ]; then \
-	     install_name_tool -id $(ildir)/libwcs.6.4.dylib \
-	                           $(ildir)/libwcs.6.4.dylib; \
-	   fi \
-	&& echo "WCSLIB $(wcslib-version)" > $@
+                       --without-pgplot $$fortranopt)
+	if [ x$(on_mac_os) = xyes ]; then
+	  install_name_tool -id $(ildir)/libwcs.6.4.dylib \
+	                        $(ildir)/libwcs.6.4.dylib
+	fi
+	echo "WCSLIB $(wcslib-version)" > $@
 
 
 
@@ -846,51 +777,58 @@ $(ibidir)/wcslib: $(ibidir)/cfitsio \
 # Astrometry-net contains a lot of programs. We need to specify the
 # installation directory and the Python executable (by default it will look
 # for /usr/bin/python)
-$(ibidir)/astrometrynet: $(ibidir)/gsl \
-                         $(ibidir)/swig \
-                         $(ipydir)/numpy \
-                         $(ibidir)/cairo \
-                         $(ibidir)/libpng \
-                         $(ibidir)/netpbm \
-                         $(ibidir)/wcslib \
-                         $(ibidir)/cfitsio \
-                         $(ibidir)/libjpeg \
-                         $(tdir)/astrometry.net-$(astrometrynet-version).tar.gz
+$(ibidir)/astrometrynet-$(astrometrynet-version): \
+                        $(ibidir)/gsl-$(gsl-version) \
+                        $(ibidir)/swig-$(swig-version) \
+                        $(ipydir)/numpy-$(numpy-version) \
+                        $(ibidir)/cairo-$(cairo-version) \
+                        $(ibidir)/libpng-$(libpng-version) \
+                        $(ibidir)/netpbm-$(netpbm-version) \
+                        $(ibidir)/wcslib-$(wcslib-version) \
+                        $(ibidir)/cfitsio-$(cfitsio-version) \
+                        $(ibidir)/libjpeg-$(libjpeg-version)
+
+        # Import the tarball
+	tarball=astrometry.net-$(astrometrynet-version).tar.gz
+	$(call import-source, $(astrometrynet-url), $(astrometrynet-checksum))
+
         # We are modifying the Makefile in two steps because on Mac OS
         # system we do not have `/proc/cpuinfo' nor `free'. Since this is
         # only for the `report.txt', this changes do not causes problems in
         # running `astrometrynet'
-	cd $(ddir) \
-	&& rm -rf astrometry.net-$(astrometrynet-version) \
-	&& if ! tar xf $(word 1,$(filter $(tdir)/%,$^)); then \
-	      echo; echo "Tar error"; exit 1; \
-	   fi \
-	&& cd astrometry.net-$(astrometrynet-version) \
-	&& sed -e 's|cat /proc/cpuinfo|echo "Ignoring CPU info"|' \
-	       -e 's|-free|echo "Ignoring RAM info"|' Makefile > Makefile.tmp \
-	&& mv Makefile.tmp Makefile \
-	&& make \
-	&& make py \
-	&& make extra \
-	&& make install INSTALL_DIR=$(idir) PYTHON_SCRIPT="$(ibdir)/python" \
-	&& cd .. \
-	&& rm -rf astrometry.net-$(astrometrynet-version) \
-	&& cp $(dtexdir)/astrometrynet.tex $(ictdir)/ \
-	&& echo "Astrometry.net $(astrometrynet-version) \citep{astrometrynet}" > $@
-
-$(ibidir)/autoconf: $(tdir)/autoconf-$(autoconf-version).tar.lz
-	$(call gbuild, autoconf-$(autoconf-version), static, ,V=1) \
-	&& echo "GNU Autoconf $(autoconf-version)" > $@
-
-$(ibidir)/automake: $(ibidir)/autoconf \
-                    $(tdir)/automake-$(automake-version).tar.gz
-	$(call gbuild, automake-$(automake-version), static, ,V=1) \
-	&& echo "GNU Automake $(automake-version)" > $@
-
-$(ibidir)/bison: $(ibidir)/help2man \
-                 $(tdir)/bison-$(bison-version).tar.xz
-	$(call gbuild, bison-$(bison-version), static, ,V=1) \
-	&& echo "GNU Bison $(bison-version)" > $@
+	cd $(ddir)
+	rm -rf astrometry.net-$(astrometrynet-version)
+	tar xf $(tdir)/$$tarball
+	cd astrometry.net-$(astrometrynet-version)
+	sed -e 's|cat /proc/cpuinfo|echo "Ignoring CPU info"|' \
+	    -e 's|-free|echo "Ignoring RAM info"|' Makefile > Makefile.tmp
+	mv Makefile.tmp Makefile
+	make
+	make py
+	make extra
+	make install INSTALL_DIR=$(idir) PYTHON_SCRIPT="$(ibdir)/python"
+	cd ..
+	rm -rf astrometry.net-$(astrometrynet-version)
+	cp $(dtexdir)/astrometrynet.tex $(ictdir)/
+	echo "Astrometry.net $(astrometrynet-version) \citep{astrometrynet}" > $@
+
+$(ibidir)/autoconf-$(autoconf-version):
+	tarball=autoconf-$(autoconf-version).tar.lz
+	$(call import-source, $(autoconf-url), $(autoconf-checksum))
+	$(call gbuild, autoconf-$(autoconf-version), static, ,V=1)
+	echo "GNU Autoconf $(autoconf-version)" > $@
+
+$(ibidir)/automake-$(automake-version): $(ibidir)/autoconf-$(autoconf-version)
+	tarball=automake-$(automake-version).tar.gz
+	$(call import-source, $(automake-url), $(automake-checksum))
+	$(call gbuild, automake-$(automake-version), static, ,V=1)
+	echo "GNU Automake $(automake-version)" > $@
+
+$(ibidir)/bison-$(bison-version): $(ibidir)/help2man-$(help2man-version)
+	tarball=bison-$(bison-version).tar.xz
+	$(call import-source, $(bison-url), $(bison-checksum))
+	$(call gbuild, bison-$(bison-version), static, ,V=1 -j$(numthreads))
+	echo "GNU Bison $(bison-version)" > $@
 
 # cdsclient is a set of software written in c to interact with astronomical
 # database servers. It is a dependency of `scamp' to be able to download
@@ -899,57 +837,69 @@ $(ibidir)/bison: $(ibidir)/help2man \
 # programs are scripts and we need to touch them before installing.
 # Otherwise this software will be re-built each time the configure step is
 # invoked.
-$(ibidir)/cdsclient: $(tdir)/cdsclient-$(cdsclient-version).tar.gz
-	cd $(ddir) \
-	&& tar xf $(word 1,$(filter $(tdir)/%,$^)) \
-	&& cd cdsclient-$(cdsclient-version) \
-	&& touch * \
-	&& ./configure --prefix=$(idir) \
-	&& make \
-	&& make install \
-	&& cd .. \
-	&& rm -rf cdsclient-$(cdsclient-version) \
-	&& echo "cdsclient $(cdsclient-version)" > $@
+$(ibidir)/cdsclient-$(cdsclient-version):
+	tarball=cdsclient-$(cdsclient-version).tar.gz
+	$(call import-source, $(cdsclient-url), $(cdsclient-checksum))
+	cd $(ddir)
+	tar xf $(tdir)/$$tarball
+	cd cdsclient-$(cdsclient-version)
+	touch *
+	./configure --prefix=$(idir)
+	make
+	make install
+	cd ..
+	rm -rf cdsclient-$(cdsclient-version)
+	echo "cdsclient $(cdsclient-version)" > $@
 
 # CMake can be built with its custom `./bootstrap' script.
-$(ibidir)/cmake: $(ibidir)/curl \
-                 $(tdir)/cmake-$(cmake-version).tar.gz
+$(ibidir)/cmake-$(cmake-version): $(ibidir)/curl-$(curl-version)
+        # Import the tarball
+	tarball=cmake-$(cmake-version).tar.gz
+	$(call import-source, $(cmake-url), $(cmake-checksum))
+
         # After searching in `bootstrap', I couldn't find `LIBS', only
         # `LDFLAGS'. So the extra libraries are being added to `LDFLAGS',
         # not `LIBS'.
         #
         # On Mac systems, the build complains about `clang' specific
         # features, so we can't use our own GCC build here.
-	if [ x$(on_mac_os) = xyes ]; then \
-	  export CC=clang; \
-	  export CXX=clang++; \
-	fi; \
-	cd $(ddir) \
-	&& rm -rf cmake-$(cmake-version) \
-	&& tar xf $(word 1,$(filter $(tdir)/%,$^)) \
-	&& cd cmake-$(cmake-version) \
-	&& ./bootstrap --prefix=$(idir) --system-curl --system-zlib \
-	               --system-bzip2 --system-liblzma --no-qt-gui \
-	               --parallel=$(numthreads) \
-	&& make -j$(numthreads) LIBS="$$LIBS -lssl -lcrypto -lz" VERBOSE=1  \
-	&& make install \
-	&& cd .. \
-	&& rm -rf cmake-$(cmake-version) \
-	&& echo "CMake $(cmake-version)" > $@
-
-$(ibidir)/flex: $(ibidir)/bison \
-                $(tdir)/flex-$(flex-version).tar.gz
-	$(call gbuild, flex-$(flex-version), static, ,V=1) \
-	&& echo "Flex $(flex-version)" > $@
-
-$(ibidir)/gdb: $(ibidir)/python \
-               $(tdir)/gdb-$(gdb-version).tar.gz
-	$(call gbuild, gdb-$(gdb-version),,,V=1) \
-	&& echo "GNU Project Debugger (GDB) $(gdb-version)" > $@
-
-$(ibidir)/ghostscript: $(ibidir)/libpng \
-                       $(ibidir)/libtiff \
-                       $(tdir)/ghostscript-$(ghostscript-version).tar.gz
+	if [ x$(on_mac_os) = xyes ]; then
+	  export CC=clang
+	  export CXX=clang++
+	fi
+	cd $(ddir)
+	rm -rf cmake-$(cmake-version)
+	tar xf $(tdir)/$$tarball
+	cd cmake-$(cmake-version)
+	./bootstrap --prefix=$(idir) --system-curl --system-zlib \
+	            --system-bzip2 --system-liblzma --no-qt-gui \
+	            --parallel=$(numthreads)
+	make -j$(numthreads) LIBS="$$LIBS -lssl -lcrypto -lz" VERBOSE=1
+	make install
+	cd ..
+	rm -rf cmake-$(cmake-version)
+	echo "CMake $(cmake-version)" > $@
+
+$(ibidir)/flex-$(flex-version): $(ibidir)/bison-$(bison-version)
+	tarball=flex-$(flex-version).tar.lz
+	$(call import-source, $(flex-url), $(flex-checksum))
+	$(call gbuild, flex-$(flex-version), static, ,V=1 -j$(numthreads))
+	echo "Flex $(flex-version)" > $@
+
+$(ibidir)/gdb-$(gdb-version): $(ibidir)/python-$(python-version)
+	tarball=gdb-$(gdb-version).tar.gz
+	$(call import-source, $(gdb-url), $(gdb-checksum))
+	$(call gbuild, gdb-$(gdb-version),,,V=1 -j$(numthreads))
+	echo "GNU Project Debugger (GDB) $(gdb-version)" > $@
+
+$(ibidir)/ghostscript-$(ghostscript-version): \
+                      $(ibidir)/libpng-$(libpng-version) \
+                      $(ibidir)/libtiff-$(libtiff-version)
+
+        # Import the tarball.
+	tarball=ghostscript-$(ghostscript-version).tar.gz
+	$(call import-source, $(ghostscript-url), $(ghostscript-checksum))
+
         # First we need to make sure some necessary X11 libraries that we
         # don't yet install in this template are present on the host
         # system, see https://savannah.nongnu.org/task/?15481 .
@@ -986,35 +936,38 @@ $(ibidir)/ghostscript: $(ibidir)/libpng \
 	fi
 
         # If they were present, go onto building Ghostscript.
-	$(call gbuild, ghostscript-$(ghostscript-version)) \
-	&& echo "GPL Ghostscript $(ghostscript-version)" > $@
-
-$(ibidir)/gnuastro: $(ibidir)/gsl \
-                    $(ibidir)/wcslib \
-                    $(ibidir)/libjpeg \
-                    $(ibidir)/libtiff \
-                    $(ibidir)/libgit2 \
-                    $(ibidir)/ghostscript \
-                    $(tdir)/gnuastro-$(gnuastro-version).tar.lz
-ifeq ($(static_build),yes)
-	staticopts="--enable-static=yes --enable-shared=no";
-endif
-	$(call gbuild, gnuastro-$(gnuastro-version), static, \
-	               $$staticopts, -j$(numthreads)) \
-	&& cp $(dtexdir)/gnuastro.tex $(ictdir)/ \
-	&& echo "GNU Astronomy Utilities $(gnuastro-version) \citep{gnuastro}" > $@
-
-$(ibidir)/help2man: $(tdir)/help2man-$(help2man-version).tar.xz
-	$(call gbuild, help2man-$(help2man-version), static, ,V=1) \
-	&& echo "Help2man $(Help2man-version)" > $@
-
-$(ibidir)/imagemagick: $(ibidir)/zlib \
-                       $(ibidir)/libjpeg \
-                       $(ibidir)/libtiff \
-                       $(tdir)/imagemagick-$(imagemagick-version).tar.xz
+	$(call gbuild, ghostscript-$(ghostscript-version),,,V=1 -j$(numthreads))
+	echo "GPL Ghostscript $(ghostscript-version)" > $@
+
+$(ibidir)/gnuastro-$(gnuastro-version): \
+                   $(ibidir)/gsl-$(gsl-version) \
+                   $(ibidir)/wcslib-$(wcslib-version) \
+                   $(ibidir)/libjpeg-$(libjpeg-version) \
+                   $(ibidir)/libtiff-$(libtiff-version) \
+                   $(ibidir)/libgit2-$(libgit2-version) \
+                   $(ibidir)/ghostscript-$(ghostscript-version)
+	tarball=gnuastro-$(gnuastro-version).tar.lz
+	$(call import-source, $(gnuastro-url), $(gnuastro-checksum))
+	$(call gbuild, gnuastro-$(gnuastro-version), static, , \
+	               -j$(numthreads))
+	cp $(dtexdir)/gnuastro.tex $(ictdir)/
+	echo "GNU Astronomy Utilities $(gnuastro-version) \citep{gnuastro}" > $@
+
+$(ibidir)/help2man-$(help2man-version):
+	tarball=help2man-$(help2man-version).tar.xz
+	$(call import-source, $(help2man-url), $(help2man-checksum))
+	$(call gbuild, help2man-$(help2man-version), static, ,V=1)
+	echo "Help2man $(Help2man-version)" > $@
+
+$(ibidir)/imagemagick-$(imagemagick-version): \
+                      $(ibidir)/zlib-$(zlib-version) \
+                      $(ibidir)/libjpeg-$(libjpeg-version) \
+                      $(ibidir)/libtiff-$(libtiff-version)
+	tarball=imagemagick-$(imagemagick-version).tar.xz
+	$(call import-source, $(imagemagick-url), $(imagemagick-checksum))
 	$(call gbuild, ImageMagick-$(imagemagick-version), static, \
-		       --without-x --disable-openmp, V=1 -j$(numthreads)) \
-	&& echo "ImageMagick $(imagemagick-version)" > $@
+		       --without-x --disable-openmp, V=1 -j$(numthreads))
+	echo "ImageMagick $(imagemagick-version)" > $@
 
 # `imfit' doesn't use the traditional `configure' and `make' to install
 # itself.  Instead of that, it uses `scons'. As a consequence, the
@@ -1025,42 +978,51 @@ $(ibidir)/imagemagick: $(ibidir)/zlib \
 # by `$(idir)'. After that, each compiled program (`imfit', `imfit-mcmc'
 # and `makeimage') is copied into the installation directory and an `rpath'
 # is added.
-$(ibidir)/imfit: $(ibidir)/gsl \
-                 $(ibidir)/fftw \
-                 $(ibidir)/scons \
-                 $(ibidir)/cfitsio \
-                 $(tdir)/imfit-$(imfit-version).tar.gz
-	cd $(ddir) \
-	&& unpackdir=imfit-$(imfit-version) \
-	&& rm -rf $$unpackdir \
-	&& if ! tar xf $(word 1,$(filter $(tdir)/%,$^)); then \
-	      echo; echo "Tar error"; exit 1; \
-	   fi \
-	&& cd $$unpackdir \
-	&& sed -i 's|/usr/local|$(idir)|g' SConstruct \
-	&& sed -i 's|/usr/include|$(idir)/include|g' SConstruct \
-	&& sed -i 's|.append(|.insert(0,|g' SConstruct \
-	&& scons --no-openmp  --no-nlopt \
-	         --cc=$(ibdir)/gcc --cpp=$(ibdir)/g++ \
-	         --header-path=$(idir)/include --lib-path=$(idir)/lib imfit \
-	&& cp imfit $(ibdir) \
-	&& scons --no-openmp  --no-nlopt\
-	         --cc=$(ibdir)/gcc --cpp=$(ibdir)/g++ \
-	         --header-path=$(idir)/include --lib-path=$(idir)/lib \
-                 imfit-mcmc \
-	&& cp imfit-mcmc $(ibdir) \
-	&& scons --no-openmp  --no-nlopt\
-	         --cc=$(ibdir)/gcc --cpp=$(ibdir)/g++ \
-	         --header-path=$(idir)/include --lib-path=$(idir)/lib \
-                 makeimage \
-	&& cp makeimage $(ibdir) \
-	&& cp $(dtexdir)/imfit.tex $(ictdir)/ \
-	&& if [ "x$(on_mac_os)" != xyes ]; then \
-	     for p in imfit imfit-mcmc makeimage; do \
-	         patchelf --set-rpath $(ildir) $(ibdir)/$$p; \
-	     done; \
-	   fi \
-	&& echo "Imfit $(imfit-version) \citep{imfit2015}" > $@
+$(ibidir)/imfit-$(imfit-version): \
+                $(ibidir)/gsl-$(gsl-version) \
+                $(ibidir)/fftw-$(fftw-version) \
+                $(ibidir)/scons-$(scons-version) \
+                $(ibidir)/cfitsio-$(cfitsio-version)
+	tarball=imfit-$(imfit-version).tar.gz
+	$(call import-source, $(imfit-url), $(imfit-checksum))
+
+        # If the C library is in a non-standard location.
+	if ! [ x$(SYS_CPATH) = x ]; then
+	  headerpath="--header-path=$(SYS_CPATH)"
+	fi
+
+        # Unpack and build imfit and its accompanying programs.
+	cd $(ddir)
+	unpackdir=imfit-$(imfit-version)
+	rm -rf $$unpackdir
+	tar xf $(tdir)/$$tarball
+	cd $$unpackdir
+	sed -i 's|/usr/local|$(idir)|g' SConstruct
+	sed -i 's|/usr/include|$(idir)/include|g' SConstruct
+	sed -i 's|.append(|.insert(0,|g' SConstruct
+	scons --no-openmp  --no-nlopt \
+	      --cc=$(ibdir)/gcc --cpp=$(ibdir)/g++ \
+	      --header-path=$(idir)/include $$headerpath \
+	      --lib-path=$(idir)/lib imfit
+	cp imfit $(ibdir)
+	scons --no-openmp  --no-nlopt \
+	      --cc=$(ibdir)/gcc --cpp=$(ibdir)/g++ \
+	      --header-path=$(idir)/include $$headerpath \
+	      --lib-path=$(idir)/lib imfit-mcmc
+	cp imfit-mcmc $(ibdir)
+	scons --no-openmp  --no-nlopt \
+	      --cc=$(ibdir)/gcc --cpp=$(ibdir)/g++ \
+	      --header-path=$(idir)/include $$headerpath \
+	      --lib-path=$(idir)/lib makeimage
+	cp makeimage $(ibdir)
+	cp $(dtexdir)/imfit.tex $(ictdir)/
+	if [ -f $(ibdir)/patchelf ]; then
+	  for p in imfit imfit-mcmc makeimage; do
+	      patchelf --set-rpath $(ildir) $(ibdir)/$$p
+	  done
+	fi
+	cp $(dtexdir)/imfit.tex $(ictdir)/
+	echo "Imfit $(imfit-version) \citep{imfit2015}" > $@
 
 # Minizip 1.x is actually distributed within zlib. It doesn't have its own
 # independent tarball. So we need a custom build, which include the GNU
@@ -1071,39 +1033,39 @@ $(ibidir)/imfit: $(ibidir)/gsl \
 #
 # About deleting the final crypt.h file after installation, see
 # https://bugzilla.redhat.com/show_bug.cgi?id=1424609
-$(ibidir)/minizip: $(ibidir)/automake \
-                   $(tdir)/zlib-$(zlib-version).tar.gz
-	cd $(ddir) \
-	&& unpackdir=minizip-$(minizip-version) \
-	&& rm -rf $$unpackdir \
-	&& mkdir $$unpackdir \
-	&& if ! tar xf $(word 1,$(filter $(tdir)/%,$^)) \
-	            -C$$unpackdir --strip-components=1; then \
-	      echo; echo "Tar error"; exit 1; \
-	   fi \
-	&& cd $$unpackdir\
-	&& ./configure --prefix=$(idir) \
-	&& make \
-	&& cd contrib/minizip \
-	&& cp Makefile Makefile.orig \
-	&& cp ../README.contrib readme.txt \
-	&& autoreconf --install \
-	&& ./configure --prefix=$(idir) \
-	&& make \
-	&& cd ../../ \
-	&& make test \
-	&& cd contrib/minizip \
-	&& make -f Makefile.orig test \
-	&& make install \
-	&& rm $(iidir)/minizip/crypt.h \
-	&& cd ../../.. \
-	&& rm -rf $$unpackdir \
-	&& echo "Minizip $(minizip-version)" > $@
-
-$(ibidir)/missfits: $(tdir)/missfits-$(missfits-version).tar.gz
-	$(call gbuild, missfits-$(missfits-version), static) \
-	&& cp $(dtexdir)/missfits.tex $(ictdir)/ \
-	&& echo "MissFITS $(missfits-version) \citep{missfits}" > $@
+$(ibidir)/minizip-$(minizip-version): $(ibidir)/automake-$(automake-version)
+	tarball=zlib-$(zlib-version).tar.gz
+	$(call import-source, $(minizip-url), $(minizip-checksum))
+	cd $(ddir)
+	unpackdir=minizip-$(minizip-version)
+	rm -rf $$unpackdir
+	mkdir $$unpackdir
+	tar xf $(tdir)/$$tarball -C$$unpackdir --strip-components=1
+	cd $$unpackdir
+	./configure --prefix=$(idir)
+	make
+	cd contrib/minizip
+	cp Makefile Makefile.orig
+	cp ../README.contrib readme.txt
+	autoreconf --install
+	./configure --prefix=$(idir)
+	make
+	cd ../../
+	make test
+	cd contrib/minizip
+	make -f Makefile.orig test
+	make install
+	rm $(iidir)/minizip/crypt.h
+	cd ../../..
+	rm -rf $$unpackdir
+	echo "Minizip $(minizip-version)" > $@
+
+$(ibidir)/missfits-$(missfits-version):
+	tarball=missfits-$(missfits-version).tar.gz
+	$(call import-source, $(missfits-url), $(missfits-checksum))
+	$(call gbuild, missfits-$(missfits-version), static)
+	cp $(dtexdir)/missfits.tex $(ictdir)/
+	echo "MissFITS $(missfits-version) \citep{missfits}" > $@
 
 # Netpbm is a prerequisite of Astrometry-net, it contains a lot of programs.
 # This program has a crazy dialogue installation which is override using the
@@ -1111,58 +1073,78 @@ $(ibidir)/missfits: $(tdir)/missfits-$(missfits-version).tar.gz
 # ask to the user. We give all answers with a pipe to the scripts (configure
 # and install). The questions are different depending on the system (tested
 # on GNU/Linux and Mac OS).
-$(ibidir)/netpbm: $(ibidir)/unzip \
-                  $(ibidir)/libpng \
-                  $(ibidir)/libjpeg \
-                  $(ibidir)/libtiff \
-                  $(ibidir)/libxml2 \
-                  $(tdir)/netpbm-$(netpbm-version).tar.gz
-	if [ x$(on_mac_os) = xyes ]; then \
-	  answers='\n\n$(ildir)\n\n\n\n\n\n$(ildir)/include\n\n$(ildir)/include\n\n$(ildir)/include\nnone\n\n'; \
-	else \
-	  answers='\n\n\n\n\n\n\n\n\n\n\n\n\nnone\n\n\n'; \
-	fi; \
-	cd $(ddir) \
-	&& unpackdir=netpbm-$(netpbm-version) \
-	&& rm -rf $$unpackdir \
-	&& if ! tar xf $(word 1,$(filter $(tdir)/%,$^)); then \
-	      echo; echo "Tar error"; exit 1; \
-	   fi \
-	&& cd $$unpackdir \
-	&& printf "$$answers" | ./configure \
-	&& make \
-	&& rm -rf $(ddir)/$$unpackdir/install \
-	&& make package pkgdir=$(ddir)/$$unpackdir/install \
-	&& printf "$(ddir)/$$unpackdir/install\n$(idir)\n\n\nN\n\n\n\n\nN\n\n" \
-	          | ./installnetpbm \
-	&& cd .. \
-	&& rm -rf $$unpackdir \
-	&& echo "Netpbm $(netpbm-version)" > $@
-
-$(ibidir)/patch: $(tdir)/patch-$(patch-version).tar.gz
-	$(call gbuild, patch-$(patch-version), static, ,V=1) \
-	&& echo "GNU Patch $(patch-version)" > $@
-
-# R programming language
-$(ibidir)/R: $(ibidir)/libpng \
-             $(ibidir)/libjpeg \
-             $(ibidir)/libtiff \
-             $(tdir)/R-$(R-version).tar.gz
-	export R_SHELL=$(SHELL); \
+$(ibidir)/netpbm-$(netpbm-version): \
+                 $(ibidir)/libpng-$(libpng-version) \
+                 $(ibidir)/libjpeg-$(libjpeg-version) \
+                 $(ibidir)/libtiff-$(libtiff-version) \
+                 $(ibidir)/libxml2-$(libxml2-version)
+	tarball=netpbm-$(netpbm-version).tar.gz
+	$(call import-source, $(netpbm-url), $(netpbm-checksum))
+	if [ x$(on_mac_os) = xyes ]; then
+	  answers='\n\n$(ildir)\n\n\n\n\n\n$(ildir)/include\n\n$(ildir)/include\n\n$(ildir)/include\nnone\n\n'
+	else
+	  answers='\n\n\n\n\n\n\n\n\n\n\n\n\nnone\n\n\n'
+	fi
+	cd $(ddir)
+	unpackdir=netpbm-$(netpbm-version)
+	rm -rf $$unpackdir
+	tar xf $(tdir)/$$tarball
+	cd $$unpackdir
+	printf "$$answers" | ./configure
+	make
+	rm -rf $(ddir)/$$unpackdir/install
+	make package pkgdir=$(ddir)/$$unpackdir/install
+	printf "$(ddir)/$$unpackdir/install\n$(idir)\n\n\nN\n\n\n\n\nN\n\n" \
+	       | ./installnetpbm
+	cd ..
+	rm -rf $$unpackdir
+	echo "Netpbm $(netpbm-version)" > $@
+
+$(ibidir)/patch-$(patch-version):
+	tarball=patch-$(patch-version).tar.gz
+	$(call import-source, $(patch-url), $(patch-checksum))
+	$(call gbuild, patch-$(patch-version), static, ,V=1)
+	echo "GNU Patch $(patch-version)" > $@
+
+$(ibidir)/pcre-$(pcre-version):
+	tarball=pcre-$(pcre-version).tar.gz
+	$(call import-source, $(pcre-url), $(pcre-checksum))
+	$(call gbuild, pcre-$(pcre-version), static, \
+	               --enable-pcretest-libreadline \
+	               --enable-unicode-properties \
+	               --includedir=$(iidir)/pcre \
+	               --enable-pcregrep-libbz2 \
+	               --enable-pcregrep-libz \
+	               , V=1 -j$(numthreads))
+	echo "Perl Compatible Regular Expressions $(pcre-version)" > $@
+
+$(ibidir)/R-$(R-version): \
+            $(ibidir)/pcre-$(pcre-version) \
+            $(ibidir)/cairo-$(cairo-version) \
+            $(ibidir)/libpng-$(libpng-version) \
+            $(ibidir)/libjpeg-$(libjpeg-version) \
+            $(ibidir)/libtiff-$(libtiff-version) \
+            $(ibidir)/libpaper-$(libpaper-version)
+	tarball=R-$(R-version).tar.gz
+	$(call import-source, $(R-url), $(R-checksum))
+
+	export R_SHELL=$(SHELL)
 	$(call gbuild, R-$(R-version), static, \
                        --without-x --with-readline \
-	               --disable-openmp) \
-	&& echo "R $(R-version)" > $@
+	               --disable-openmp, -j$(numthreads))
+	echo "R $(R-version)" > $@
 
 # SCAMP documentation says ATLAS is a mandatory prerequisite for using
 # SCAMP. We have ATLAS into the project but there are some problems with the
 # libraries that are not yet solved. However, we tried to install it with
 # the option --enable-openblas and it worked (same issue happened with
 # `sextractor'.
-$(ibidir)/scamp: $(ibidir)/fftw \
-                 $(ibidir)/openblas \
-                 $(ibidir)/cdsclient \
-                 $(tdir)/scamp-$(scamp-version).tar.lz
+$(ibidir)/scamp-$(scamp-version): \
+                $(ibidir)/fftw-$(fftw-version) \
+                $(ibidir)/openblas-$(openblas-version) \
+                $(ibidir)/cdsclient-$(cdsclient-version)
+	tarball=scamp-$(scamp-version).tar.lz
+	$(call import-source, $(scamp-url), $(scamp-checksum))
 	$(call gbuild, scamp-$(scamp-version), static, \
                    --enable-threads \
                    --enable-openblas \
@@ -1170,84 +1152,90 @@ $(ibidir)/scamp: $(ibidir)/fftw \
                    --with-fftw-libdir=$(idir) \
                    --with-fftw-incdir=$(idir)/include \
                    --with-openblas-libdir=$(ildir) \
-                   --with-openblas-incdir=$(idir)/include) \
-	&& cp $(dtexdir)/scamp.tex $(ictdir)/ \
-	&& echo "SCAMP $(scamp-version) \citep{scamp}" > $@
+                   --with-openblas-incdir=$(idir)/include)
+	cp $(dtexdir)/scamp.tex $(ictdir)/
+	echo "SCAMP $(scamp-version) \citep{scamp}" > $@
 
 # Since `scons' doesn't use the traditional GNU installation with
 # `configure' and `make' it is installed manually using `python'.
-$(ibidir)/scons: $(ibidir)/python \
-                 $(tdir)/scons-$(scons-version).tar.gz
-	cd $(ddir) \
-	&& unpackdir=scons-$(scons-version) \
-	&& rm -rf $$unpackdir \
-	&& if ! tar xf $(word 1,$(filter $(tdir)/%,$^)); then \
-	      echo; echo "Tar error"; exit 1; \
-	   fi \
-	&& cd $$unpackdir \
-	&& python setup.py install \
-	&& echo "SCons $(scons-version)" > $@
+$(ibidir)/scons-$(scons-version): $(ibidir)/python-$(python-version)
+	tarball=scons-$(scons-version).tar.gz
+	$(call import-source, $(scons-url), $(scons-checksum))
+	cd $(ddir)
+	unpackdir=scons-$(scons-version)
+	rm -rf $$unpackdir
+	tar xf $(tdir)/$$tarball
+	cd $$unpackdir
+	python setup.py install
+	echo "SCons $(scons-version)" > $@
 
 # Sextractor crashes complaining about not linking with some ATLAS
 # libraries. But we can override this issue since we have Openblas
 # installed, it is just necessary to explicity tell sextractor to use it in
 # the configuration step.
-$(ibidir)/sextractor: $(ibidir)/fftw \
-                      $(ibidir)/openblas \
-                      $(tdir)/sextractor-$(sextractor-version).tar.lz
+$(ibidir)/sextractor-$(sextractor-version): \
+                     $(ibidir)/fftw-$(fftw-version) \
+                     $(ibidir)/openblas-$(openblas-version)
+	tarball=sextractor-$(sextractor-version).tar.lz
+	$(call import-source, $(sextractor-url), $(sextractor-checksum))
 	$(call gbuild, sextractor-$(sextractor-version), static, \
 	               --enable-threads --enable-openblas \
 	               --with-openblas-libdir=$(ildir) \
-	               --with-openblas-incdir=$(idir)/include) \
-	&& ln -fs $(ibdir)/sex $(ibdir)/sextractor \
-	&& cp $(dtexdir)/sextractor.tex $(ictdir)/ \
-	&& echo "SExtractor $(sextractor-version) \citep{sextractor}" > $@
-
-$(ibidir)/swarp: $(ibidir)/fftw \
-                 $(tdir)/swarp-$(swarp-version).tar.gz
+	               --with-openblas-incdir=$(idir)/include)
+	ln -fs $(ibdir)/sex $(ibdir)/sextractor
+	cp $(dtexdir)/sextractor.tex $(ictdir)/
+	echo "SExtractor $(sextractor-version) \citep{sextractor}" > $@
+
+$(ibidir)/swarp-$(swarp-version): $(ibidir)/fftw-$(fftw-version)
+	tarball=swarp-$(swarp-version).tar.gz
+	$(call import-source, $(swarp-url), $(swarp-checksum))
 	$(call gbuild, swarp-$(swarp-version), static, \
-                       --enable-threads) \
-	&& cp $(dtexdir)/swarp.tex $(ictdir)/ \
-	&& echo "SWarp $(swarp-version) \citep{swarp}" > $@
+                       --enable-threads)
+	cp $(dtexdir)/swarp.tex $(ictdir)/
+	echo "SWarp $(swarp-version) \citep{swarp}" > $@
 
-$(ibidir)/swig: $(tdir)/swig-$(swig-version).tar.gz
+$(ibidir)/swig-$(swig-version):
         # Option --without-pcre was a suggestion once the configure step
         # was tried and it failed. It was not recommended but it works!
         # pcr is a dependency of swig
-	$(call gbuild, swig-$(swig-version), static, --without-pcre) \
-	&& echo "Swig $(swig-version)" > $@
-
-$(ibidir)/xlsxio: $(ibidir)/cmake \
-                  $(ibidir)/expat \
-                  $(ibidir)/minizip \
-                  $(tdir)/xlsxio-$(xlsxio-version).tar.gz
-	if [ x$(on_mac_os) = xyes ]; then \
-	  export CC=clang; \
-	  export CXX=clang++; \
-	  export LDFLAGS="$$LDFLAGS -lbz2"; \
-	else \
-	  export LDFLAGS="$$LDFLAGS -lbz2 -lbsd"; \
-	fi; \
+	tarball=swig-$(swig-version).tar.gz
+	$(call import-source, $(swig-url), $(swig-checksum))
+	$(call gbuild, swig-$(swig-version), static, --without-pcre)
+	echo "Swig $(swig-version)" > $@
+
+$(ibidir)/xlsxio-$(xlsxio-version): \
+                 $(ibidir)/cmake-$(cmake-version) \
+                 $(ibidir)/expat-$(expat-version) \
+                 $(ibidir)/minizip-$(minizip-version)
+	tarball=xlsxio-$(xlsxio-version).tar.gz
+	$(call import-source, $(xlsxio-url), $(xlsxio-checksum))
+	if [ x$(on_mac_os) = xyes ]; then
+	  export CC=clang
+	  export CXX=clang++
+	  export LDFLAGS="$$LDFLAGS -lbz2"
+	else
+	  export LDFLAGS="$$LDFLAGS -lbz2 -lbsd"
+	fi
 	$(call cbuild, xlsxio-$(xlsxio-version), static, \
 	       -DMINIZIP_DIR:PATH=$(idir) \
 	       -DMINIZIP_LIBRARIES=$(idir) \
-	       -DMINIZIP_INCLUDE_DIRS=$(iidir)) \
-	&& echo "Correcting internal linking of XLSX I/O executables..." \
-	&& if [ "x$(on_mac_os)" = xyes ]; then \
-	     for f in $(ibdir)/xlsxio_* $(ildir)/libxlsxio_*.dylib; do \
-	       install_name_tool -change  libxlsxio_read.dylib \
-	                         $(ildir)/libxlsxio_read.dylib $$f; \
-	       install_name_tool -change  libxlsxio_write.dylib \
-	                         $(ildir)/libxlsxio_write.dylib $$f; \
-	     done; \
-	   else \
-	     for f in $(ibdir)/xlsxio_* $(ildir)/libxlsxio_*.so; do \
-	       patchelf --set-rpath $(ildir) $$f; \
-	     done; \
-	   fi \
-	&& echo "Deleting XLSX I/O example files..." \
-	&& rm $(ibdir)/example_xlsxio_* \
-	&& echo "XLSX I/O $(xlsxio-version)" > $@
+	       -DMINIZIP_INCLUDE_DIRS=$(iidir))
+	echo "Correcting internal linking of XLSX I/O executables..."
+	if [ "x$(on_mac_os)" = xyes ]; then
+	  for f in $(ibdir)/xlsxio_* $(ildir)/libxlsxio_*.dylib; do
+	    install_name_tool -change  libxlsxio_read.dylib \
+	                      $(ildir)/libxlsxio_read.dylib $$f
+	    install_name_tool -change  libxlsxio_write.dylib \
+	                      $(ildir)/libxlsxio_write.dylib $$f
+	  done
+	else
+	  for f in $(ibdir)/xlsxio_* $(ildir)/libxlsxio_*.so; do
+	     patchelf --set-rpath $(ildir) $$f
+	  done
+	fi
+	echo "Deleting XLSX I/O example files..."
+	rm $(ibdir)/example_xlsxio_*
+	echo "XLSX I/O $(xlsxio-version)" > $@
 
 
 
@@ -1272,11 +1260,11 @@ $(ibidir)/xlsxio: $(ibidir)/cmake \
 # (`ftp.dante.de'), however, it is far too slow (when I tested it). The
 # `rit.edu' server seems to be a good alternative (given the importance of
 # NY on the internet infrastructure).
-tlmirror=http://mirrors.rit.edu/CTAN/systems/texlive/tlnet
+texlive-url=http://mirrors.rit.edu/CTAN/systems/texlive/tlnet
+$(itidir)/texlive-ready-tlmgr: reproduce/software/config/texlive.conf
 
-# The core TeX Live system.
-$(itidir)/texlive-ready-tlmgr: reproduce/software/config/texlive.conf \
-                               $(tdir)/install-tl-unx.tar.gz
+	tarball=install-tl-unx.tar.gz
+	$(call import-source, $(texlive-url), NO-CHECK-SUM)
 
         # Unpack, enter the directory, and install based on the given
         # configuration (prerequisite of this rule).
@@ -1318,7 +1306,7 @@ $(itidir)/texlive-ready-tlmgr: reproduce/software/config/texlive.conf \
         # TeXLive using that. The old tarball will be preserved, but will
         # have an '-OLD' suffix after it.
 	if ./install-tl --profile=texlive.conf -repository \
-	                $(tlmirror) 2> log.txt; then
+	                $(texlive-url) 2> log.txt; then
 
           # Put a symbolic link of the TeX Live executables in `ibdir' to
           # avoid all the complexities of its sub-directories and additions
@@ -1368,7 +1356,7 @@ $(itidir)/texlive-ready-tlmgr: reproduce/software/config/texlive.conf \
 	          $$topdir/reproduce/software/config/texlive.conf \
 	          > texlive.conf
 	      if ./install-tl --profile=texlive.conf -repository \
-	                      $(tlmirror); then
+	                      $(texlive-url); then
 	        ln -fs $(idir)/texlive/maneage/bin/*/* $(ibdir)/
 	        echo "TeX Live is ready." > $@
 	      else
@@ -1398,15 +1386,8 @@ $(itidir)/texlive-ready-tlmgr: reproduce/software/config/texlive.conf \
 # don't currently build biber from source. So we can't choose the library
 # version. But we have the source and build instructions for the `nsl'
 # library. When we later build biber from source, we can easily use them.
-#
-#ifeq ($(on_mac_os),yes)
-#forbiber =
-#else
-#forbiber = $(ibidir)/libnsl
-#endif
 $(itidir)/texlive: reproduce/software/config/texlive-packages.conf \
-                   $(itidir)/texlive-ready-tlmgr \
-                   $(forbiber)
+                   $(itidir)/texlive-ready-tlmgr
 
         # To work with TeX live installation, we'll need the internet.
 	@res=$$(cat $(itidir)/texlive-ready-tlmgr)
@@ -1419,7 +1400,7 @@ $(itidir)/texlive: reproduce/software/config/texlive-packages.conf \
 
           # Before checking LaTeX packages, update tlmgr itself.
 	  tlmgr option backupdir $$backupdir
-	  tlmgr -repository $(tlmirror) update --self
+	  tlmgr -repository $(texlive-url) update --self
 
           # Install all the extra necessary packages. If LaTeX complains
           # about not finding a command/file/what-ever/XXXXXX, simply run
diff --git a/reproduce/software/make/python.mk b/reproduce/software/make/python.mk
index eef8279..ccfbc72 100644
--- a/reproduce/software/make/python.mk
+++ b/reproduce/software/make/python.mk
@@ -3,8 +3,12 @@
 # ------------------------------------------------------------------------
 #                      !!!!! IMPORTANT NOTES !!!!!
 #
-# This Makefile will be run by the initial `./project configure' script. It
-# is not included into the reproduction pipe after that.
+# This Makefile will be loaded into 'high-level.mk', which is called by the
+# `./project configure' script. It is not included into the project
+# afterwards.
+#
+# This Makefile contains instructions to build all the Python-related
+# software within the project.
 #
 # ------------------------------------------------------------------------
 #
@@ -52,274 +56,52 @@ python-major-version = $(shell echo $(python-version) | awk 'BEGIN{FS="."} \
 
 
 
-# Tarballs
-# --------
-#
-# All the necessary tarballs are defined and prepared with this rule.
-#
-# Note that we want the tarballs to follow the convention of NAME-VERSION
-# before the `tar.XX' prefix. For those programs that don't follow this
-# convention, but include the name/version in their tarball names with
-# another format, we'll do the modification before the download so the
-# downloaded file has our desired format.
-pytarballs = $(foreach t, asn1crypto-$(asn1crypto-version).tar.gz \
-                        asteval-$(asteval-version).tar.gz \
-                        astroquery-$(astroquery-version).tar.gz \
-                        astropy-$(astropy-version).tar.gz \
-                        beautifulsoup4-$(beautifulsoup4-version).tar.gz \
-                        certifi-$(certifi-version).tar.gz \
-                        cffi-$(cffi-version).tar.gz \
-                        chardet-$(chardet-version).tar.gz \
-                        corner-$(corner-version).tar.gz \
-                        cryptography-$(cryptography-version).tar.gz \
-                        cycler-$(cycler-version).tar.gz \
-                        cython-$(cython-version).tar.gz \
-                        eigency-$(eigency-version).tar.gz \
-                        emcee-$(emcee-version).tar.gz \
-                        esutil-$(esutil-version).tar.gz \
-                        entrypoints-$(entrypoints-version).tar.gz \
-                        flake8-$(flake8-version).tar.gz \
-                        future-$(future-version).tar.gz \
-                        galsim-$(galsim-version).tar.gz \
-                        h5py-$(h5py-version).tar.gz \
-                        html5lib-$(html5lib-version).tar.gz \
-                        idna-$(idna-version).tar.gz \
-                        jeepney-$(jeepney-version).tar.gz \
-                        kiwisolver-$(kiwisolver-version).tar.gz \
-                        keyring-$(keyring-version).tar.gz \
-                        libffi-$(libffi-version).tar.gz \
-                        lmfit-$(lmfit-version).tar.gz \
-                        lsstdesccoord-$(lsstdesccoord-version).tar.gz \
-                        matplotlib-$(matplotlib-version).tar.gz \
-                        mpi4py-$(mpi4py-version).tar.gz \
-                        mpmath-$(mpmath-version).tar.gz \
-                        numpy-$(numpy-version).zip \
-                        pkgconfig-$(pypkgconfig-version).tar.gz \
-                        pip-$(pip-version).tar.gz \
-                        pexpect-$(pexpect-version).tar.gz \
-                        pybind11-$(pybind11-version).tar.gz \
-                        pycodestyle-$(pycodestyle-version).tar.gz \
-                        pycparser-$(pycparser-version).tar.gz \
-                        pyflakes-$(pyflakes-version).tar.gz \
-                        python-$(python-version).tar.gz \
-                        python-dateutil-$(python-dateutil-version).tar.gz \
-                        pyparsing-$(pyparsing-version).tar.gz \
-                        pyyaml-$(pyyaml-version).tar.gz \
-                        requests-$(requests-version).tar.gz \
-                        scipy-$(scipy-version).tar.gz \
-                        secretstorage-$(secretstorage-version).tar.gz \
-                        setuptools-$(setuptools-version).zip \
-                        setuptools_scm-$(setuptools_scm-version).tar.gz \
-                        sip_tpv-$(sip_tpv-version).tar.gz \
-                        six-$(six-version).tar.gz \
-                        soupsieve-$(soupsieve-version).tar.gz \
-                        sympy-$(sympy-version).tar.gz \
-                        uncertainties-$(uncertainties-version).tar.gz \
-                        urllib3-$(urllib3-version).tar.gz \
-                        webencodings-$(webencodings-version).tar.gz \
-                        virtualenv-$(virtualenv-version).tar.gz \
-                      , $(tdir)/$(t) )
-pytopurl=https://files.pythonhosted.org/packages
-$(pytarballs): $(tdir)/%:
-
-        # Convenience variable
-        # --------------------
-        #
-        # `n' is just for convenience and to avoid having to repeat the
-        # package tarball name in the conditional to find its URL.
-        #
-        # For some packages (for example `python-dateutil', or those with
-        # a number or dash in their name), we need special consideration
-        # because the tokenization above will produce `python' as the
-        # first string.
-	@if [ $* = python-dateutil-$(python-dateutil-version).tar.gz ]; then
-	  n=dateutil
-
-        # elif [ $* = strange-tarball5name-version.tar.gz ]; then
-        #  n=strange5-name
-	else
-          # Remove the version numbers and suffix from the tarball name so
-          # we can search more easily only with the program name. This
-          # requires the first character of the version to be a digit:
-          # packages such as `foo' and `foo-3' will not be distinguished,
-          # but `foo' and `foo2' will be distinguished.
-	  n=$$(echo $* | sed -e's/-[0-9]/ /' -e's/\./ /g' \
-	               | awk '{print $$1}' )
-
-	fi
-
-        # Set the top download link of the requested tarball. The ones
-        # that have non-standard filenames (differing from our archived
-        # tarball names) are treated first, then the standard ones.
-	mergenames=1
-	if [ $$n = cython ]; then
-	  mergenames=0
-	  c=$(cython-checksum)
-	  hash=36/da/fcb979fc8cb486a67a013d6aefefbb95a3e19e67e49dff8a35e014046c5e
-	  h=$(pytopurl)/$$hash/Cython-$(cython-version).tar.gz
-	elif [ $$n = galsim ]; then
-	  mergenames=0
-	  c=$(galsim-checksum)
-	  hash=8f/3b/bbc7cff7590d3624d528564f08745f071e316c67fce154ad38210833c103
-	  h=$(pytopurl)/$$hash/GalSim-$(galsim-version).tar.gz
-	elif [ $$n = lsstdesccoord ]; then
-	  mergenames=0
-	  c=$(lsstdesccoord-checksum)
-	  hash=9d/39/ad17697571c9aed36d20ed9ae0a135e3a734fb7f15a8605f92bf27c3b02c
-	  h=$(pytopurl)/$$hash/LSSTDESC.Coord-$(lsstdesccoord-version).tar.gz
-	elif [ $$n = python ]; then
-	  mergenames=0
-	  c=$(python-checksum)
-	  h=https://www.python.org/ftp/python/$(python-version)/Python-$(python-version).tgz
-	elif [ $$n = pyyaml ]; then
-	  mergenames=0
-	  c=$(pyyaml-checksum)
-	  hash=9f/2c/9417b5c774792634834e730932745bc09a7d36754ca00acf1ccd1ac2594d
-	  h=$(pytopurl)/$$hash/PyYAML-$(pyyaml-version).tar.gz
-	elif [ $$n = libffi ]; then
-	  mergenames=0
-	  c=$(libffi-checksum)
-	  h=ftp://sourceware.org/pub/libffi/libffi-$(libffi-version).tar.gz
-	elif [ $$n = secretstorage  ]; then
-	  mergenames=0
-	  c=$(secretstorage-checksum)
-	  hash=a6/89/df343dbc2957a317127e7ff2983230dc5336273be34f2e1911519d85aeb5
-	  h=$(pytopurl)/$$hash/SecretStorage-$(secretstorage-version).tar.gz
-	elif [ $$n = asn1crypto     ]; then h=fc/f1/8db7daa71f414ddabfa056c4ef792e1461ff655c2ae2928a2b675bfed6b4; c=$(asn1crypto-checksum)
-	elif [ $$n = asteval        ]; then h=50/3f/29b7935c6dc09ee96dc347edc66c57e8ef68d595dd35b763a36a117acc8c; c=$(asteval-checksum)
-	elif [ $$n = astroquery     ]; then h=e2/af/a3cd3b30745832a0e81f5f13327234099aaf5d03b7979ac947a888e68e91; c=$(astroquery-checksum)
-	elif [ $$n = astropy        ]; then h=de/96/7feaca4b9be134128838395a9d924ea0b389ed4381702dcd9d11ae31789f; c=$(astropy-checksum)
-	elif [ $$n = beautifulsoup4 ]; then h=80/f2/f6aca7f1b209bb9a7ef069d68813b091c8c3620642b568dac4eb0e507748; c=$(beautifulsoup4-checksum)
-	elif [ $$n = certifi        ]; then h=55/54/3ce77783acba5979ce16674fc98b1920d00b01d337cfaaf5db22543505ed; c=$(certifi-checksum)
-	elif [ $$n = cffi           ]; then h=64/7c/27367b38e6cc3e1f49f193deb761fe75cda9f95da37b67b422e62281fcac; c=$(cffi-checksum)
-	elif [ $$n = chardet        ]; then h=fc/bb/a5768c230f9ddb03acc9ef3f0d4a3cf93462473795d18e9535498c8f929d; c=$(chardet-checksum)
-	elif [ $$n = corner         ]; then h=65/af/a7ba022f2d5787f51db91b5550cbe8e8c40a6eebd8f15119e743a09a9c19; c=$(corner-checksum)
-	elif [ $$n = cryptography   ]; then h=07/ca/bc827c5e55918ad223d59d299fff92f3563476c3b00d0a9157d9c0217449; c=$(cryptography-checksum)
-	elif [ $$n = cycler         ]; then h=c2/4b/137dea450d6e1e3d474e1d873cd1d4f7d3beed7e0dc973b06e8e10d32488; c=$(cycler-checksum)
-	elif [ $$n = eigency        ]; then h=fb/6e/bc4359fbfb0bb0b588ec328251b0d0836bdd7c0a4c568959ea06df023e18; c=$(eigency-checksum)
-	elif [ $$n = emcee          ]; then h=f0/c0/cd433f2aedeef9b1e5ed7d236c82564f7518fe7fe2238fa141ea9ce08e73; c=$(emcee-checksum)
-	elif [ $$n = entrypoints    ]; then h=b4/ef/063484f1f9ba3081e920ec9972c96664e2edb9fdc3d8669b0e3b8fc0ad7c; c=$(entrypoints-checksum)
-	elif [ $$n = esutil         ]; then h=5b/91/77e38282fd3d47b55e351544ab179eb209b309a8d2d40f8cdb6241beda00; c=$(esutil-checksum)
-	elif [ $$n = flake8         ]; then h=8d/a7/99222c9200af533c1ecb1120d99adbd1c033b57296ac5cb39d121db007a8; c=$(flake8-checksum)
-	elif [ $$n = future         ]; then h=3f/bf/57733d44afd0cf67580658507bd11d3ec629612d5e0e432beb4b8f6fbb04; c=$(future-checksum)
-	elif [ $$n = h5py           ]; then h=43/27/a6e7dcb8ae20a4dbf3725321058923fec262b6f7835179d78ccc8d98deec; c=$(h5py-checksum)
-	elif [ $$n = html5lib       ]; then h=85/3e/cf449cf1b5004e87510b9368e7a5f1acd8831c2d6691edd3c62a0823f98f; c=$(html5lib-checksum)
-	elif [ $$n = idna           ]; then h=ad/13/eb56951b6f7950cadb579ca166e448ba77f9d24efc03edd7e55fa57d04b7; c=$(idna-checksum)
-	elif [ $$n = jeepney        ]; then h=16/1d/74adf3b164a8d19a60d0fcf706a751ffa2a1eaa8e5bbb1b6705c92a05263; c=$(jeepney-checksum)
-	elif [ $$n = keyring        ]; then h=15/88/c6ce9509438bc02d54cf214923cfba814412f90c31c95028af852b19f9b2; c=$(keyring-checksum)
-	elif [ $$n = kiwisolver     ]; then h=31/60/494fcce70d60a598c32ee00e71542e52e27c978e5f8219fae0d4ac6e2864; c=$(kiwisolver-checksum)
-	elif [ $$n = lmfit          ]; then h=59/6e/117794cf85b7345361877e49245870490ae438f1981dea3c6af1316b30e7; c=$(lmfit-checksum)
-	elif [ $$n = matplotlib     ]; then h=12/d1/7b12cd79c791348cb0c78ce6e7d16bd72992f13c9f1e8e43d2725a6d8adf; c=$(matplotlib-checksum)
-	elif [ $$n = mpi4py         ]; then h=04/f5/a615603ce4ab7f40b65dba63759455e3da610d9a155d4d4cece1d8fd6706; c=$(mpi4py-checksum)
-	elif [ $$n = mpmath         ]; then h=ca/63/3384ebb3b51af9610086b23ea976e6d27d6d97bf140a76a365bd77a3eb32; c=$(mpmath-checksum)
-	elif [ $$n = numpy          ]; then h=ac/36/325b27ef698684c38b1fe2e546e2e7ef9cecd7037bcdb35c87efec4356af; c=$(numpy-checksum)
-	elif [ $$n = pexpect        ]; then h=1c/b1/362a0d4235496cb42c33d1d8732b5e2c607b0129ad5fdd76f5a583b9fcb3; c=$(pexpect-checksum)
-	elif [ $$n = pip            ]; then h=4c/4d/88bc9413da11702cbbace3ccc51350ae099bb351febae8acc85fec34f9af; c=$(pip-checksum)
-	elif [ $$n = pkgconfig      ]; then h=6e/a9/ff67ef67217dfdf2aca847685fe789f82b931a6957a3deac861297585db6; c=$(pypkgconfig-checksum)
-	elif [ $$n = pybind11       ]; then h=aa/91/deb6743e79e22ab01502296570b39b8404f10cc507a6692d612a7fee8d51; c=$(pybind11-checksum)
-	elif [ $$n = pycodestyle    ]; then h=1c/d1/41294da5915f4cae7f4b388cea6c2cd0d6cd53039788635f6875dfe8c72f; c=$(pycodestyle-checksum)
-	elif [ $$n = pycparser      ]; then h=68/9e/49196946aee219aead1290e00d1e7fdeab8567783e83e1b9ab5585e6206a; c=$(pycparser-checksum)
-	elif [ $$n = pyflakes       ]; then h=52/64/87303747635c2988fcaef18af54bfdec925b6ea3b80bcd28aaca5ba41c9e; c=$(pyflakes-checksum)
-	elif [ $$n = pyparsing      ]; then h=b9/b8/6b32b3e84014148dcd60dd05795e35c2e7f4b72f918616c61fdce83d27fc; c=$(pyparsing-checksum)
-	elif [ $$n = dateutil       ]; then h=ad/99/5b2e99737edeb28c71bcbec5b5dda19d0d9ef3ca3e92e3e925e7c0bb364c; c=$(python-dateutil-checksum)
-	elif [ $$n = requests       ]; then h=52/2c/514e4ac25da2b08ca5a464c50463682126385c4272c18193876e91f4bc38; c=$(requests-checksum)
-	elif [ $$n = scipy          ]; then h=ee/5b/5afcd1c46f97b3c2ac3489dbc95d6ca28eacf8e3634e51f495da68d97f0f; c=$(scipy-checksum)
-	elif [ $$n = secretstorage  ]; then h=a6/89/df343dbc2957a317127e7ff2983230dc5336273be34f2e1911519d85aeb5; c=$(secretstorage-checksum)
-	elif [ $$n = setuptools     ]; then h=11/0a/7f13ef5cd932a107cd4c0f3ebc9d831d9b78e1a0e8c98a098ca17b1d7d97; c=$(setuptools-checksum)
-	elif [ $$n = setuptools_scm ]; then h=83/44/53cad68ce686585d12222e6769682c4bdb9686808d2739671f9175e2938b; c=$(setuptools_scm-checksum)
-	elif [ $$n = six            ]; then h=dd/bf/4138e7bfb757de47d1f4b6994648ec67a51efe58fa907c1e11e350cddfca; c=$(six-checksum)
-	elif [ $$n = sip_tpv        ]; then h=27/93/a973aab2a3bf0c12cb385611819710921e13b090304c6bd015026cf9c502; c=$(sip_tpv-checksum)
-	elif [ $$n = soupsieve      ]; then h=0c/52/e9088bb9b96e2d39fc3b33fcda5b4fde9d71473536ac660a1ca9a0958a2f; c=$(soupsieve-checksum)
-	elif [ $$n = sympy          ]; then h=54/2e/6adb11fe599d4cfb7e8833753350ac51aa2c0603c226b36f9051cc9d2425; c=$(sympy-checksum)
-	elif [ $$n = uncertainties  ]; then h=2a/c2/babbe5b16141859dd799ed31c03987100a7b6d0ca7c0ed4429c96ce60fdf; c=$(uncertainties-checksum)
-	elif [ $$n = urllib3        ]; then h=b1/53/37d82ab391393565f2f831b8eedbffd57db5a718216f82f1a8b4d381a1c1; c=$(urllib3-checksum)
-	elif [ $$n = virtualenv     ]; then h=51/aa/c395a6e6eaaedfa5a04723b6446a1df783b16cca6fec66e671cede514688; c=$(virtualenv-checksum)
-	elif [ $$n = webencodings   ]; then h=0b/02/ae6ceac1baeda530866a85075641cec12989bd8d31af6d5ab4a3e8c92f47; c=$(webencodings-checksum)
-#	elif [ $$n = strange5-name  ]; then h=XXXXX; c=$(XXXXX-checksum)
-	else
-	  echo; echo; echo;
-	  echo "'$$n' not recognized as a dependency name to download."
-	  echo; echo; echo;
-	  exit 1
-	fi
-
-        # Download the requested tarball. Note that some packages may not
-        # follow our naming convention (where the package name is merged
-        # with its version number). In such cases, `w' will be the full
-        # address, not just the top directory address. But since we are
-        # storing all the tarballs in one directory, we want it to have
-        # the same naming convention, so we'll download it to a temporary
-        # name, then rename that.
-	rm -f "$@.unchecked"
-	if [ -f $(DEPENDENCIES-DIR)/$* ]; then
-	  cp $(DEPENDENCIES-DIR)/$* "$@.unchecked"
-	else
-	  if [ $$mergenames = 1 ]; then  tarballurl=$(pytopurl)/$$h/"$*"
-	  else                           tarballurl=$$h
-	  fi
-
-          # Download using the script specially defined for this job.
-	  touch $(lockdir)/download
-	  downloader="wget --no-use-server-timestamps -O"
-	  $(downloadwrapper) "$$downloader" $(lockdir)/download \
-	                     $$tarballurl "$@.unchecked" "$(backupservers)"
-	fi
-
-        # Make sure this is the expected tarball. Note that we now have a
-        # controlled `sha512sum' build (as part of GNU Coreutils). So we
-        # don't need to check its existance like `basic.mk'.
-	checksum=$$(sha512sum "$@.unchecked" | awk '{print $$1}')
-	if [ x"$$checksum" = x"$$c" ]; then
-	  mv "$@.unchecked" "$@"
-	else
-	  echo "ERROR: Non-matching checksum for '$*'."
-	  echo "Checksum should be: $$c"
-	  echo "Checksum is:        $$checksum"
-	  exit 1
-	fi
-
-
-
-
-
 # Necessary programs and libraries
 # --------------------------------
 #
 # While this Makefile is for Python programs, in some cases, we need
 # certain programs (like Python itself), or libraries for the modules.
-$(ibidir)/libffi: $(tdir)/libffi-$(libffi-version).tar.gz
+$(ibidir)/libffi-$(libffi-version):
+        # Prepare the source.
+	tarball=libffi-$(libffi-version).tar.gz
+	$(call import-source, $(libffi-url), $(libffi-checksum))
+
+        # Build libffi.
+	$(call gbuild, libffi-$(libffi-version), , \
+                       CFLAGS="-DNO_JAVA_RAW_API=1")
 
         # On some Fedora systems, libffi installs in `lib64', not
         # `lib'. This will cause problems when building setuptools
         # later. To fix this problem, we'll first check if this has indeed
         # happened (it exists under `lib64', but not under `lib'). If so,
         # we'll put a copy of the installed libffi libraries in `lib'.
-	$(call gbuild, libffi-$(libffi-version), , \
-                       CFLAGS="-DNO_JAVA_RAW_API=1") \
-	&& if [ -f $(idir)/lib64/libffi.a ] \
-	      && ! [ -f $(idir)/lib/libffi.a ]; then \
-	        cp $(idir)/lib64/libffi* $(ildir)/; \
-	   fi \
-	&& echo "Libffi $(libffi-version)" > $@
-
-$(ibidir)/python: $(ibidir)/libffi \
-                  $(tdir)/python-$(python-version).tar.gz
+	if [ -f $(idir)/lib64/libffi.a ] && ! [ -f $(idir)/lib/libffi.a ]; then
+	  cp $(idir)/lib64/libffi* $(ildir)/
+	fi
+	echo "Libffi $(libffi-version)" > $@
+
+$(ibidir)/python-$(python-version): $(ibidir)/libffi-$(libffi-version)
+
+        # Download the source.
+	tarball=python-$(python-version).tar.gz
+	$(call import-source, $(python-url), $(python-checksum))
+
         # On Mac systems, the build complains about `clang' specific
         # features, so we can't use our own GCC build here.
-	if [ x$(on_mac_os) = xyes ]; then \
-	  export CC=clang; \
-	  export CXX=clang++; \
-	fi; \
+	if [ x$(on_mac_os) = xyes ]; then
+	  export CC=clang
+	  export CXX=clang++
+	fi
 	$(call gbuild, Python-$(python-version),, \
 	       --without-ensurepip \
 	       --with-system-ffi \
-	       --enable-shared) \
-	&& ln -sf $(ildir)/python$(python-major-version)  $(ildir)/python \
-	&& ln -sf $(ibdir)/python$(python-major-version)  $(ibdir)/python \
-	&& ln -sf $(iidir)/python$(python-major-version)m $(iidir)/python$(python-major-version) \
-	&& rm -rf $(ipydir) \
-	&& mkdir $(ipydir) \
-	&& echo "Python $(python-version)" > $@
+	       --enable-shared, -j$(numthreads))
+	ln -sf $(ildir)/python$(python-major-version)  $(ildir)/python
+	ln -sf $(ibdir)/python$(python-major-version)  $(ibdir)/python
+	ln -sf $(iidir)/python$(python-major-version)m $(iidir)/python$(python-major-version)
+	rm -rf $(ipydir)
+	mkdir $(ipydir)
+	echo "Python $(python-version)" > $@
 
 
 
@@ -343,22 +125,22 @@ $(ibidir)/python: $(ibidir)/libffi \
 #   pyhook_before: optional steps before running `python setup.py build'
 #   pyhook_after: optional steps after running `python setup.py install'
 pybuild = cd $(ddir); rm -rf $(2); \
-	 if ! $(1) $(word 1,$(filter $(tdir)/%,$^)); then \
-	   echo; echo "Tar error"; exit 1; \
-	 fi; \
-	 cd $(2); \
-	 if [ "x$(strip $(3))" != x ]; then \
-	   sed -e 's|@LIBDIR[@]|'"$(ildir)"'|' \
-	       -e 's|@INCDIR[@]|'"$(idir)/include"'|' \
-	       $(3) > site.cfg; \
-	 fi; \
-	 if type pyhook_before &>/dev/null; then pyhook_before; fi \
-	 && python setup.py build \
-	 && python setup.py install \
-	 && if type pyhook_after &>/dev/null; then pyhook_after; fi \
-	 && cd .. \
-	 && rm -rf $(2) \
-	 && echo "$(4)" > $@
+	if ! $(1) $(tdir)/$$tarball; then \
+	  echo; echo "Tar error"; exit 1; \
+	fi; \
+	cd $(2); \
+	if [ "x$(strip $(3))" != x ]; then \
+	  sed -e 's|@LIBDIR[@]|'"$(ildir)"'|' \
+	      -e 's|@INCDIR[@]|'"$(idir)/include"'|' \
+	      $(3) > site.cfg; \
+	fi; \
+	if type pyhook_before &>/dev/null; then pyhook_before; fi; \
+	python setup.py build; \
+	python setup.py install; \
+	if type pyhook_after &>/dev/null; then pyhook_after; fi; \
+	cd ..; \
+	rm -rf $(2); \
+	echo "$(4)" > $@
 
 
 
@@ -368,31 +150,40 @@ pybuild = cd $(ddir); rm -rf $(2); \
 # ---------------
 #
 # All the necessary Python modules go here.
-$(ipydir)/asn1crypto: $(ipydir)/setuptools \
-                      $(tdir)/asn1crypto-$(asn1crypto-version).tar.gz
+$(ipydir)/asn1crypto-$(asn1crypto-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=asn1crypto-$(asn1crypto-version).tar.gz
+	$(call import-source, $(asn1crypto-url), $(asn1crypto-checksum))
 	$(call pybuild, tar xf, asn1crypto-$(asn1crypto-version), , \
 	                Asn1crypto $(asn1crypto-version))
 
-$(ipydir)/asteval: $(ipydir)/numpy \
-                   $(tdir)/asteval-$(asteval-version).tar.gz
+$(ipydir)/asteval-$(asteval-version): $(ipydir)/numpy-$(numpy-version)
+	tarball=asteval-$(asteval-version).tar.gz
+	$(call import-source, $(asteval-url), $(asteval-checksum))
 	$(call pybuild, tar xf, asteval-$(asteval-version), , \
 	                ASTEVAL $(asteval-version))
 
-$(ipydir)/astroquery: $(ipydir)/astropy \
-                      $(ipydir)/keyring \
-                      $(ipydir)/requests \
-                      $(tdir)/astroquery-$(astroquery-version).tar.gz
-	$(call pybuild, tar xf, astroquery-$(astroquery-version), ,\
+$(ipydir)/astroquery-$(astroquery-version): \
+                     $(ipydir)/astropy-$(astropy-version) \
+                     $(ipydir)/keyring-$(keyring-version) \
+                     $(ipydir)/requests-$(requests-version)
+	tarball=astroquery-$(astroquery-version).tar.gz
+	$(call import-source, $(astroquery-url), $(astroquery-checksum))
+	$(call pybuild, tar xf, astroquery-$(astroquery-version), , \
 	                Astroquery $(astroquery-version))
 
-$(ipydir)/astropy: $(ipydir)/h5py \
-                   $(ibidir)/expat \
-                   $(ipydir)/scipy \
-                   $(ipydir)/numpy \
-                   $(ipydir)/pyyaml \
-                   $(ipydir)/html5lib \
-                   $(ipydir)/beautifulsoup4 \
-                   $(tdir)/astropy-$(astropy-version).tar.gz
+$(ipydir)/astropy-$(astropy-version): \
+                  $(ipydir)/h5py-$(h5py-version) \
+                  $(ibidir)/expat-$(expat-version) \
+                  $(ipydir)/scipy-$(scipy-version) \
+                  $(ipydir)/numpy-$(numpy-version) \
+                  $(ipydir)/pyyaml-$(pyyaml-version) \
+                  $(ipydir)/html5lib-$(html5lib-version) \
+                  $(ipydir)/beautifulsoup4-$(beautifulsoup4-version)
+
+        # Download the source.
+	tarball=astropy-$(astropy-version).tar.gz
+	$(call import-source, $(astropy-url), $(astropy-checksum))
+
         # Currently, when the Expat library is already built in a project
         # (for example as a dependency of another program), Astropy's
         # internal building of Expat will conflict with the project's. So
@@ -404,107 +195,133 @@ $(ipydir)/astropy: $(ipydir)/h5py \
 	  echo "[build]"            >> setup.cfg
 	  echo "use_system_expat=1" >> setup.cfg
 	}
-	$(call pybuild, tar xf, astropy-$(astropy-version)) \
-	&& cp $(dtexdir)/astropy.tex $(ictdir)/ \
-	&& echo "Astropy $(astropy-version) \citep{astropy2013,astropy2018}" > $@
-
-$(ipydir)/beautifulsoup4: $(ipydir)/soupsieve \
-                          $(tdir)/beautifulsoup4-$(beautifulsoup4-version).tar.gz
-	$(call pybuild, tar xf, beautifulsoup4-$(beautifulsoup4-version), ,\
+	$(call pybuild, tar xf, astropy-$(astropy-version))
+	cp $(dtexdir)/astropy.tex $(ictdir)/
+	echo "Astropy $(astropy-version) \citep{astropy2013,astropy2018}" > $@
+
+$(ipydir)/beautifulsoup4-$(beautifulsoup4-version): \
+                         $(ipydir)/soupsieve-$(soupsieve-version)
+	tarball=beautifulsoup4-$(beautifulsoup4-version).tar.gz
+	$(call import-source, $(beautifulsoup4-url), $(beautifulsoup4-checksum))
+	$(call pybuild, tar xf, beautifulsoup4-$(beautifulsoup4-version), , \
 	                BeautifulSoup $(beautifulsoup4-version))
 
-$(ipydir)/certifi: $(ipydir)/setuptools \
-                   $(tdir)/certifi-$(certifi-version).tar.gz
-	$(call pybuild, tar xf, certifi-$(certifi-version), ,\
+$(ipydir)/certifi-$(certifi-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=certifi-$(certifi-version).tar.gz
+	$(call import-source, $(certifi-url), $(certifi-checksum))
+	$(call pybuild, tar xf, certifi-$(certifi-version), , \
 	                Certifi $(certifi-version))
 
-$(ipydir)/cffi: $(ibidir)/libffi \
-                $(ipydir)/pycparser \
-                $(tdir)/cffi-$(cffi-version).tar.gz
-	$(call pybuild, tar xf, cffi-$(cffi-version), ,\
-	                cffi $(cffi-version))
-
-$(ipydir)/chardet: $(ipydir)/setuptools \
-                   $(tdir)/chardet-$(chardet-version).tar.gz
-	$(call pybuild, tar xf, chardet-$(chardet-version), ,\
+$(ipydir)/cffi-$(cffi-version): \
+               $(ibidir)/libffi-$(libffi-version) \
+               $(ipydir)/pycparser-$(pycparser-version)
+	tarball=cffi-$(cffi-version).tar.gz
+	$(call import-source, $(cffi-url), $(cffi-checksum))
+	$(call pybuild, tar xf, cffi-$(cffi-version), ,cffi $(cffi-version))
+
+$(ipydir)/chardet-$(chardet-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=chardet-$(chardet-version).tar.gz
+	$(call import-source, $(chardet-url), $(chardet-checksum))
+	$(call pybuild, tar xf, chardet-$(chardet-version), , \
 	                Chardet $(chardet-version))
 
-$(ipydir)/corner: $(ipydir)/matplotlib \
-                  $(tdir)/corner-$(corner-version).tar.gz
-	$(call pybuild, tar xf, corner-$(corner-version), ,\
-	                Corner $(corner-version)) \
-	&& cp $(dtexdir)/corner.tex $(ictdir)/ \
-	&& echo "Corner $(corner-version) \citep{corner}" > $@
-
-$(ipydir)/cryptography: $(ipydir)/cffi \
-                        $(ipydir)/asn1crypto \
-                        $(tdir)/cryptography-$(cryptography-version).tar.gz
-	$(call pybuild, tar xf, cryptography-$(cryptography-version), ,\
+$(ipydir)/corner-$(corner-version): $(ipydir)/matplotlib-$(matplotlib-version)
+	tarball=corner-$(corner-version).tar.gz
+	$(call import-source, $(corner-url), $(corner-checksum))
+	$(call pybuild, tar xf, corner-$(corner-version), , \
+	                Corner $(corner-version))
+	cp $(dtexdir)/corner.tex $(ictdir)/
+	echo "Corner $(corner-version) \citep{corner}" > $@
+
+$(ipydir)/cryptography-$(cryptography-version): \
+                       $(ipydir)/cffi-$(cffi-version) \
+                       $(ipydir)/asn1crypto-$(asn1crypto-version)
+	tarball=cryptography-$(cryptography-version).tar.gz
+	$(call import-source, $(cryptography-url), $(cryptography-checksum))
+	$(call pybuild, tar xf, cryptography-$(cryptography-version), , \
 	                Cryptography $(cryptography-version))
 
-$(ipydir)/cycler: $(ipydir)/six \
-                  $(tdir)/cycler-$(cycler-version).tar.gz
-	$(call pybuild, tar xf, cycler-$(cycler-version), ,\
+$(ipydir)/cycler-$(cycler-version): $(ipydir)/six-$(six-version)
+	tarball=cycler-$(cycler-version).tar.gz
+	$(call import-source, $(cycler-url), $(cycler-checksum))
+	$(call pybuild, tar xf, cycler-$(cycler-version), , \
 	                Cycler $(cycler-version))
 
-$(ipydir)/cython: $(ipydir)/setuptools \
-                  $(tdir)/cython-$(cython-version).tar.gz
-	$(call pybuild, tar xf, Cython-$(cython-version)) \
-	&& cp $(dtexdir)/cython.tex $(ictdir)/ \
-	&& echo "Cython $(cython-version) \citep{cython2011}" > $@
-
-$(ipydir)/esutil: $(ipydir)/numpy \
-                  $(tdir)/esutil-$(esutil-version).tar.gz
-	$(call pybuild, tar xf, esutil-$(esutil-version), ,\
+$(ipydir)/cython-$(cython-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=cython-$(cython-version).tar.gz
+	$(call import-source, $(cython-url), $(cython-checksum))
+	$(call pybuild, tar xf, Cython-$(cython-version))
+	cp $(dtexdir)/cython.tex $(ictdir)/
+	echo "Cython $(cython-version) \citep{cython2011}" > $@
+
+$(ipydir)/esutil-$(esutil-version): $(ipydir)/numpy-$(numpy-version)
+	tarball=esutil-$(esutil-version).tar.gz
+	$(call import-source, $(esutil-url), $(esutil-checksum))
+	$(call pybuild, tar xf, esutil-$(esutil-version), , \
 	                esutil $(esutil-version))
 
-$(ipydir)/eigency: $(ibidir)/eigen \
-                   $(tdir)/eigency-$(eigency-version).tar.gz
-	$(call pybuild, tar xf, eigency-$(eigency-version), ,\
+$(ipydir)/eigency-$(eigency-version): \
+                  $(ipydir)/numpy-$(numpy-version) \
+                  $(ibidir)/eigen-$(eigen-version) \
+                  $(ipydir)/cython-$(cython-version)
+	tarball=eigency-$(eigency-version).tar.gz
+	$(call import-source, $(eigency-url), $(eigency-checksum))
+	$(call pybuild, tar xf, eigency-$(eigency-version), , \
 	                eigency $(eigency-version))
 
-$(ipydir)/emcee: $(ipydir)/numpy \
-                 $(ipydir)/setuptools_scm \
-                 $(tdir)/emcee-$(emcee-version).tar.gz
-	$(call pybuild, tar xf, emcee-$(emcee-version), ,\
+$(ipydir)/emcee-$(emcee-version): \
+                $(ipydir)/numpy-$(numpy-version) \
+                $(ipydir)/setuptools_scm-$(setuptools_scm-version)
+	tarball=emcee-$(emcee-version).tar.gz
+	$(call import-source, $(emcee-url), $(emcee-checksum))
+	$(call pybuild, tar xf, emcee-$(emcee-version), , \
 	                emcee $(emcee-version))
 
-$(ipydir)/entrypoints: $(ipydir)/setuptools \
-                       $(tdir)/entrypoints-$(entrypoints-version).tar.gz
-	$(call pybuild, tar xf, entrypoints-$(entrypoints-version), ,\
+$(ipydir)/entrypoints-$(entrypoints-version): \
+                      $(ipydir)/setuptools-$(setuptools-version)
+	tarball=entrypoints-$(entrypoints-version).tar.gz
+	$(call import-source, $(entrypoints-url), $(entrypoints-checksum))
+	$(call pybuild, tar xf, entrypoints-$(entrypoints-version), , \
 	                EntryPoints $(entrypoints-version))
 
-$(ipydir)/flake8: $(ipydir)/pyflakes \
-                  $(ipydir)/pycodestyle \
-                  $(tdir)/flake8-$(flake8-version).tar.gz
-	$(call pybuild, tar xf, flake8-$(flake8-version), ,\
+$(ipydir)/flake8-$(flake8-version): \
+                 $(ipydir)/pyflakes-$(pyflakes-version) \
+                 $(ipydir)/pycodestyle-$(pycodestyle-version)
+	tarball=flake8-$(flake8-version).tar.gz
+	$(call import-source, $(flake8-url), $(flake8-checksum))
+	$(call pybuild, tar xf, flake8-$(flake8-version), , \
 	                Flake8 $(flake8-version))
 
-$(ipydir)/future: $(ipydir)/setuptools \
-                  $(tdir)/future-$(future-version).tar.gz
-	$(call pybuild, tar xf, future-$(future-version), ,\
+$(ipydir)/future-$(future-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=future-$(future-version).tar.gz
+	$(call import-source, $(future-url), $(future-checksum))
+	$(call pybuild, tar xf, future-$(future-version), , \
 	                Future $(future-version))
 
-$(ipydir)/galsim: $(ipydir)/future \
-                  $(ipydir)/astropy \
-                  $(ipydir)/eigency \
-                  $(ipydir)/pybind11 \
-                  $(ipydir)/lsstdesccoord \
-                  $(tdir)/galsim-$(galsim-version).tar.gz
-	$(call pybuild, tar xf, GalSim-$(galsim-version)) \
-	&& cp $(dtexdir)/galsim.tex $(ictdir)/ \
-	&& echo "Galsim $(galsim-version) \citep{galsim}" > $@
-
-$(ipydir)/h5py: $(ipydir)/six \
-                $(ibidir)/hdf5 \
-                $(ipydir)/numpy \
-                $(ipydir)/cython \
-                $(ipydir)/mpi4py \
-                $(ipydir)/pypkgconfig \
-                $(tdir)/h5py-$(h5py-version).tar.gz
-	export HDF5_MPI=ON; \
-	export HDF5_DIR=$(ildir); \
-	$(call pybuild, tar xf, h5py-$(h5py-version), ,\
+$(ipydir)/galsim-$(galsim-version): \
+                 $(ipydir)/future-$(future-version) \
+                 $(ipydir)/astropy-$(astropy-version) \
+                 $(ipydir)/eigency-$(eigency-version) \
+                 $(ipydir)/pybind11-$(pybind11-version) \
+                 $(ipydir)/lsstdesccoord-$(lsstdesccoord-version)
+	tarball=galsim-$(galsim-version).tar.gz
+	$(call import-source, $(galsim-url), $(galsim-checksum))
+	$(call pybuild, tar xf, GalSim-$(galsim-version))
+	cp $(dtexdir)/galsim.tex $(ictdir)/
+	echo "Galsim $(galsim-version) \citep{galsim}" > $@
+
+$(ipydir)/h5py-$(h5py-version): \
+               $(ipydir)/six-$(six-version) \
+               $(ibidir)/hdf5-$(hdf5-version) \
+               $(ipydir)/numpy-$(numpy-version) \
+               $(ipydir)/cython-$(cython-version) \
+               $(ipydir)/mpi4py-$(mpi4py-version) \
+               $(ipydir)/pypkgconfig-$(pypkgconfig-version)
+	export HDF5_MPI=ON
+	export HDF5_DIR=$(ildir)
+	tarball=h5py-$(h5py-version).tar.gz
+	$(call import-source, $(h5py-url), $(h5py-checksum))
+	$(call pybuild, tar xf, h5py-$(h5py-version), , \
 	                h5py $(h5py-version))
 
 # `healpy' is actually installed as part of the HEALPix package. It will be
@@ -514,231 +331,283 @@ $(ipydir)/h5py: $(ipydir)/six \
 # and just ask for `healpy'. To avoid confusion in such cases, we'll just
 # set `healpy' to be dependent on `healpix' and not download any tarball
 # for it, or write anything in the final target.
-$(ipydir)/healpy: $(ibidir)/healpix
+$(ipydir)/healpy-$(healpy-version): $(ibidir)/healpix-$(healpy-version)
 	touch $@
 
-$(ipydir)/html5lib: $(ipydir)/six \
-                    $(ipydir)/webencodings \
-                    $(tdir)/html5lib-$(html5lib-version).tar.gz
-	$(call pybuild, tar xf, html5lib-$(html5lib-version), ,\
+$(ipydir)/html5lib-$(html5lib-version): \
+                   $(ipydir)/six-$(six-version) \
+                   $(ipydir)/webencodings-$(webencodings-version)
+	tarball=html5lib-$(html5lib-version).tar.gz
+	$(call import-source, $(html5lib-url), $(html5lib-checksum))
+	$(call pybuild, tar xf, html5lib-$(html5lib-version), , \
 	                HTML5lib $(html5lib-version))
 
-$(ipydir)/idna: $(ipydir)/setuptools \
-                $(tdir)/idna-$(idna-version).tar.gz
-	$(call pybuild, tar xf, idna-$(idna-version), ,\
+$(ipydir)/idna-$(idna-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=idna-$(idna-version).tar.gz
+	$(call import-source, $(idna-url), $(idna-checksum))
+	$(call pybuild, tar xf, idna-$(idna-version), , \
 	       idna $(idna-version))
 
-$(ipydir)/jeepney: $(ipydir)/setuptools \
-                   $(tdir)/jeepney-$(jeepney-version).tar.gz
-	$(call pybuild, tar xf, jeepney-$(jeepney-version), ,\
+$(ipydir)/jeepney-$(jeepney-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=jeepney-$(jeepney-version).tar.gz
+	$(call import-source, $(jeepney-url), $(jeepney-checksum))
+	$(call pybuild, tar xf, jeepney-$(jeepney-version), , \
 	                Jeepney $(jeepney-version))
 
-$(ipydir)/keyring: $(ipydir)/entrypoints \
-                   $(ipydir)/secretstorage \
-                   $(ipydir)/setuptools_scm \
-                   $(tdir)/keyring-$(keyring-version).tar.gz
-	$(call pybuild, tar xf, keyring-$(keyring-version), ,\
+$(ipydir)/keyring-$(keyring-version): \
+                  $(ipydir)/entrypoints-$(entrypoints-version) \
+                  $(ipydir)/secretstorage-$(secretstorage-version) \
+                  $(ipydir)/setuptools_scm-$(setuptools_scm-version)
+	tarball=keyring-$(keyring-version).tar.gz
+	$(call import-source, $(keyring-url), $(keyring-checksum))
+	$(call pybuild, tar xf, keyring-$(keyring-version), , \
 	                Keyring $(keyring-version))
 
-$(ipydir)/kiwisolver: $(ipydir)/setuptools \
-                      $(tdir)/kiwisolver-$(kiwisolver-version).tar.gz
-	$(call pybuild, tar xf, kiwisolver-$(kiwisolver-version), ,\
+$(ipydir)/kiwisolver-$(kiwisolver-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=kiwisolver-$(kiwisolver-version).tar.gz
+	$(call import-source, $(kiwisolver-url), $(kiwisolver-checksum))
+	$(call pybuild, tar xf, kiwisolver-$(kiwisolver-version), , \
 	                Kiwisolver $(kiwisolver-version))
 
-$(ipydir)/lmfit: $(ipydir)/six \
-                 $(ipydir)/scipy \
-                 $(ipydir)/emcee \
-                 $(ipydir)/corner \
-                 $(ipydir)/asteval \
-                 $(ipydir)/matplotlib \
-                 $(ipydir)/uncertainties \
-                 $(tdir)/lmfit-$(lmfit-version).tar.gz
-	$(call pybuild, tar xf, lmfit-$(lmfit-version), ,\
+$(ipydir)/lmfit-$(lmfit-version): \
+                $(ipydir)/six-$(six-version) \
+                $(ipydir)/scipy-$(scipy-version) \
+                $(ipydir)/emcee-$(emcee-version) \
+                $(ipydir)/corner-$(corner-version) \
+                $(ipydir)/asteval-$(asteval-version) \
+                $(ipydir)/matplotlib-$(matplotlib-version) \
+                $(ipydir)/uncertainties-$(uncertainties-version)
+	tarball=lmfit-$(lmfit-version).tar.gz
+	$(call import-source, $(lmfit-url), $(lmfit-checksum))
+	$(call pybuild, tar xf, lmfit-$(lmfit-version), , \
 	                LMFIT $(lmfit-version))
 
-$(ipydir)/lsstdesccoord: $(ipydir)/setuptools \
-                         $(tdir)/lsstdesccoord-$(lsstdesccoord-version).tar.gz
-	$(call pybuild, tar xf, LSSTDESC.Coord-$(lsstdesccoord-version), ,\
+$(ipydir)/lsstdesccoord-$(lsstdesccoord-version): \
+                        $(ipydir)/setuptools-$(setuptools-version)
+	tarball=lsstdesccoord-$(lsstdesccoord-version).tar.gz
+	$(call import-source, $(lsstdesccoord-url), $(lsstdesccoord-checksum))
+	$(call pybuild, tar xf, LSSTDESC.Coord-$(lsstdesccoord-version), , \
 	                LSSTDESC.Coord $(lsstdesccoord-version))
 
-$(ipydir)/matplotlib: $(ipydir)/numpy \
-                      $(ipydir)/cycler \
-                      $(itidir)/texlive \
-                      $(ibidir)/freetype \
-                      $(ipydir)/pyparsing \
-                      $(ipydir)/kiwisolver \
-                      $(ibidir)/ghostscript \
-                      $(ibidir)/imagemagick \
-                      $(ipydir)/python-dateutil \
-                      $(tdir)/matplotlib-$(matplotlib-version).tar.gz
+$(ipydir)/matplotlib-$(matplotlib-version): \
+                     $(itidir)/texlive \
+                     $(ipydir)/numpy-$(numpy-version) \
+                     $(ipydir)/cycler-$(cycler-version) \
+                     $(ibidir)/freetype-$(freetype-version) \
+                     $(ipydir)/pyparsing-$(pyparsing-version) \
+                     $(ipydir)/kiwisolver-$(kiwisolver-version) \
+                     $(ibidir)/ghostscript-$(ghostscript-version) \
+                     $(ibidir)/imagemagick-$(imagemagick-version) \
+                     $(ipydir)/python-dateutil-$(python-dateutil-version)
+
+        # Download the source.
+	tarball=matplotlib-$(matplotlib-version).tar.gz
+	$(call import-source, $(matplotlib-url), $(matplotlib-checksum))
+
         # On Mac systems, the build complains about `clang' specific
         # features, so we can't use our own GCC build here.
-	if [ x$(on_mac_os) = xyes ]; then \
-	  export CC=clang; \
-	  export CXX=clang++; \
-	fi; \
-	$(call pybuild, tar xf, matplotlib-$(matplotlib-version)) \
-	&& cp $(dtexdir)/matplotlib.tex $(ictdir)/ \
-	&& echo "Matplotlib $(matplotlib-version) \citep{matplotlib2007}" > $@
-
-$(ipydir)/mpi4py: $(ibidir)/openmpi \
-                  $(ipydir)/setuptools \
-                  $(tdir)/mpi4py-$(mpi4py-version).tar.gz
-	$(call pybuild, tar xf, mpi4py-$(mpi4py-version)) \
-	&& cp $(dtexdir)/mpi4py.tex $(ictdir)/ \
-	&& echo "mpi4py $(mpi4py-version) \citep{mpi4py2011}" > $@
-
-$(ipydir)/mpmath: $(ipydir)/setuptools \
-                  $(tdir)/mpmath-$(mpmath-version).tar.gz
-	$(call pybuild, tar xf, mpmath-$(mpmath-version), ,\
+	if [ x$(on_mac_os) = xyes ]; then
+	  export CC=clang
+	  export CXX=clang++
+	fi
+	$(call pybuild, tar xf, matplotlib-$(matplotlib-version))
+	cp $(dtexdir)/matplotlib.tex $(ictdir)/
+	echo "Matplotlib $(matplotlib-version) \citep{matplotlib2007}" > $@
+
+$(ipydir)/mpi4py-$(mpi4py-version): \
+                 $(ibidir)/openmpi-$(openmpi-version) \
+                 $(ipydir)/setuptools-$(setuptools-version)
+	tarball=mpi4py-$(mpi4py-version).tar.gz
+	$(call import-source, $(mpi4py-url), $(mpi4py-checksum))
+	$(call pybuild, tar xf, mpi4py-$(mpi4py-version))
+	cp $(dtexdir)/mpi4py.tex $(ictdir)/
+	echo "mpi4py $(mpi4py-version) \citep{mpi4py2011}" > $@
+
+$(ipydir)/mpmath-$(mpmath-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=mpmath-$(mpmath-version).tar.gz
+	$(call import-source, $(mpmath-url), $(mpmath-checksum))
+	$(call pybuild, tar xf, mpmath-$(mpmath-version), , \
 	                mpmath $(mpmath-version))
 
-$(ipydir)/numpy: $(ibidir)/unzip \
-                 $(ibidir)/openblas \
-                 $(ipydir)/setuptools \
-                 $(tdir)/numpy-$(numpy-version).zip
-	if [ x$(on_mac_os) = xyes ]; then \
-	  export LDFLAGS="$(LDFLAGS) -undefined dynamic_lookup -bundle"; \
-	else \
-	  export LDFLAGS="$(LDFLAGS) -shared"; \
-	fi; \
-	export CFLAGS="--std=c99 $$CFLAGS"; \
-	conf="$$(pwd)/reproduce/software/config/numpy-scipy.cfg"; \
+$(ipydir)/numpy-$(numpy-version): \
+                $(ibidir)/unzip-$(unzip-version) \
+                $(ibidir)/openblas-$(openblas-version) \
+                $(ipydir)/setuptools-$(setuptools-version)
+	tarball=numpy-$(numpy-version).zip
+	$(call import-source, $(numpy-url), $(numpy-checksum))
+	if [ x$(on_mac_os) = xyes ]; then
+	  export LDFLAGS="$(LDFLAGS) -undefined dynamic_lookup -bundle"
+	else
+	  export LDFLAGS="$(LDFLAGS) -shared"
+	fi
+	export CFLAGS="--std=c99 $$CFLAGS"
+	conf="$$(pwd)/reproduce/software/config/numpy-scipy.cfg"
 	$(call pybuild, unzip, numpy-$(numpy-version),$$conf, \
-	                Numpy $(numpy-version)) \
-	&& cp $(dtexdir)/numpy.tex $(ictdir)/ \
-	&& echo "Numpy $(numpy-version) \citep{numpy2011}" > $@
-
-$(ipydir)/pexpect: $(ipydir)/setuptools \
-                   $(tdir)/pexpect-$(pexpect-version).tar.gz
-	$(call pybuild, tar xf, pexpect-$(pexpect-version), ,\
+	                Numpy $(numpy-version))
+	cp $(dtexdir)/numpy.tex $(ictdir)/
+	echo "Numpy $(numpy-version) \citep{numpy2011}" > $@
+
+$(ipydir)/pexpect-$(pexpect-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=pexpect-$(pexpect-version).tar.gz
+	$(call import-source, $(pexpect-url), $(pexpect-checksum))
+	$(call pybuild, tar xf, pexpect-$(pexpect-version), , \
 	                Pexpect $(pexpect-version))
 
-$(ibidir)/pip3: $(ipydir)/setuptools \
-                $(tdir)/pip-$(pip-version).tar.gz
-	$(call pybuild, tar xf, pip-$(pip-version), ,\
+$(ipydir)/pip-$(pip-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=pip-$(pip-version).tar.gz
+	$(call import-source, $(pip-url), $(pip-checksum))
+	$(call pybuild, tar xf, pip-$(pip-version), , \
 	                PiP $(pip-version))
 
-$(ipydir)/pycodestyle: $(ipydir)/setuptools \
-                       $(tdir)/pycodestyle-$(pycodestyle-version).tar.gz
-	$(call pybuild, tar xf, pycodestyle-$(pycodestyle-version), ,\
+$(ipydir)/pycodestyle-$(pycodestyle-version): \
+                      $(ipydir)/setuptools-$(setuptools-version)
+	tarball=pycodestyle-$(pycodestyle-version).tar.gz
+	$(call import-source, $(pycodestyle-url), $(pycodestyle-checksum))
+	$(call pybuild, tar xf, pycodestyle-$(pycodestyle-version), , \
 	                pycodestyle $(pycodestyle-version))
 
-$(ipydir)/pybind11: $(ibidir)/eigen \
-                    $(ibidir)/boost \
-                    $(ipydir)/setuptools \
-                    $(tdir)/pybind11-$(pybind11-version).tar.gz
+$(ipydir)/pybind11-$(pybind11-version): \
+                   $(ibidir)/eigen-$(eigen-version) \
+                   $(ibidir)/boost-$(boost-version) \
+                   $(ipydir)/setuptools-$(setuptools-version)
+	tarball=pybind11-$(pybind11-version).tar.gz
+	$(call import-source, $(pybind11-url), $(pybind11-checksum))
 	pyhook_after() {
 	  cp -r include/pybind11 $(iidir)/python$(python-major-version)m/
 	}
-	$(call pybuild, tar xf, pybind11-$(pybind11-version), ,\
+	$(call pybuild, tar xf, pybind11-$(pybind11-version), , \
 	                pybind11 $(pybind11-version))
 
-$(ipydir)/pycparser: $(ipydir)/setuptools \
-                     $(tdir)/pycparser-$(pycparser-version).tar.gz
-	$(call pybuild, tar xf, pycparser-$(pycparser-version), ,\
+$(ipydir)/pycparser-$(pycparser-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=pycparser-$(pycparser-version).tar.gz
+	$(call import-source, $(pycparser-url), $(pycparser-checksum))
+	$(call pybuild, tar xf, pycparser-$(pycparser-version), , \
 	                pycparser $(pycparser-version))
 
-$(ipydir)/pyflakes: $(ipydir)/setuptools \
-                    $(tdir)/pyflakes-$(pyflakes-version).tar.gz
-	$(call pybuild, tar xf, pyflakes-$(pyflakes-version), ,\
+$(ipydir)/pyflakes-$(pyflakes-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=pyflakes-$(pyflakes-version).tar.gz
+	$(call import-source, $(pyflakes-url), $(pyflakes-checksum))
+	$(call pybuild, tar xf, pyflakes-$(pyflakes-version), , \
 	                pyflakes $(pyflakes-version))
 
-$(ipydir)/pyparsing: $(ipydir)/setuptools \
-                     $(tdir)/pyparsing-$(pyparsing-version).tar.gz
-	$(call pybuild, tar xf, pyparsing-$(pyparsing-version), ,\
+$(ipydir)/pyparsing-$(pyparsing-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=pyparsing-$(pyparsing-version).tar.gz
+	$(call import-source, $(pyparsing-url), $(pyparsing-checksum))
+	$(call pybuild, tar xf, pyparsing-$(pyparsing-version), , \
 	                PyParsing $(pyparsing-version))
 
-$(ipydir)/pypkgconfig: $(ipydir)/setuptools \
-                       $(tdir)/pkgconfig-$(pypkgconfig-version).tar.gz
+$(ipydir)/pypkgconfig-$(pypkgconfig-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=pkgconfig-$(pypkgconfig-version).tar.gz
+	$(call import-source, $(pypkgconfig-url), $(pypkgconfig-checksum))
 	$(call pybuild, tar xf, pkgconfig-$(pypkgconfig-version), ,
 	                pkgconfig $(pypkgconfig-version))
 
-$(ipydir)/python-dateutil: $(ipydir)/six \
-                           $(ipydir)/setuptools_scm \
-                           $(tdir)/python-dateutil-$(python-dateutil-version).tar.gz
-	$(call pybuild, tar xf, python-dateutil-$(python-dateutil-version), ,\
+$(ipydir)/python-dateutil-$(python-dateutil-version): \
+                          $(ipydir)/six-$(six-version) \
+                          $(ipydir)/setuptools_scm-$(setuptools_scm-version)
+	tarball=python-dateutil-$(python-dateutil-version).tar.gz
+	$(call import-source, $(python-dateutil-url), $(python-dateutil-checksum))
+	$(call pybuild, tar xf, python-dateutil-$(python-dateutil-version), , \
 	                python-dateutil $(python-dateutil-version))
 
-$(ipydir)/pyyaml: $(ibidir)/yaml \
-                  $(ipydir)/cython \
-                  $(tdir)/pyyaml-$(pyyaml-version).tar.gz
-	$(call pybuild, tar xf, PyYAML-$(pyyaml-version), ,\
+$(ipydir)/pyyaml-$(pyyaml-version): \
+                 $(ibidir)/yaml-$(yaml-version) \
+                 $(ipydir)/cython-$(cython-version)
+	tarball=pyyaml-$(pyyaml-version).tar.gz
+	$(call import-source, $(pyyaml-url), $(pyyaml-checksum))
+	$(call pybuild, tar xf, PyYAML-$(pyyaml-version), , \
 	                PyYAML $(pyyaml-version))
 
-$(ipydir)/requests: $(ipydir)/idna \
-                    $(ipydir)/numpy \
-                    $(ipydir)/certifi \
-                    $(ipydir)/chardet \
-                    $(ipydir)/urllib3 \
-                    $(tdir)/requests-$(requests-version).tar.gz
-	$(call pybuild, tar xf, requests-$(requests-version), ,\
+$(ipydir)/requests-$(requests-version): $(ipydir)/idna-$(idna-version) \
+                    $(ipydir)/numpy-$(numpy-version) \
+                    $(ipydir)/certifi-$(certifi-version) \
+                    $(ipydir)/chardet-$(chardet-version) \
+                    $(ipydir)/urllib3-$(urllib3-version)
+	tarball=requests-$(requests-version).tar.gz
+	$(call import-source, $(requests-url), $(requests-checksum))
+	$(call pybuild, tar xf, requests-$(requests-version), , \
 	                Requests $(requests-version))
 
-$(ipydir)/scipy: $(ipydir)/numpy \
-                 $(tdir)/scipy-$(scipy-version).tar.gz
-	if [ x$(on_mac_os) = xyes ]; then \
-	  export LDFLAGS="$(LDFLAGS) -undefined dynamic_lookup -bundle"; \
-	else \
-	  export LDFLAGS="$(LDFLAGS) -shared"; \
-	fi; \
-	conf="$$(pwd)/reproduce/software/config/numpy-scipy.cfg"; \
-	$(call pybuild, tar xf, scipy-$(scipy-version),$$conf) \
-	&& cp $(dtexdir)/scipy.tex $(ictdir)/ \
-	&& echo "Scipy $(scipy-version) \citep{scipy2007,scipy2011}" > $@
-
-$(ipydir)/secretstorage: $(ipydir)/jeepney \
-                         $(ipydir)/cryptography \
-                         $(tdir)/secretstorage-$(secretstorage-version).tar.gz
-	$(call pybuild, tar xf, SecretStorage-$(secretstorage-version), ,\
+$(ipydir)/scipy-$(scipy-version): $(ipydir)/numpy-$(numpy-version)
+	tarball=scipy-$(scipy-version).tar.gz
+	$(call import-source, $(scipy-url), $(scipy-checksum))
+	if [ x$(on_mac_os) = xyes ]; then
+	  export LDFLAGS="$(LDFLAGS) -undefined dynamic_lookup -bundle"
+	else
+	  export LDFLAGS="$(LDFLAGS) -shared"
+	fi
+	conf="$$(pwd)/reproduce/software/config/numpy-scipy.cfg"
+	$(call pybuild, tar xf, scipy-$(scipy-version),$$conf)
+	cp $(dtexdir)/scipy.tex $(ictdir)/
+	echo "Scipy $(scipy-version) \citep{scipy2007,scipy2011}" > $@
+
+$(ipydir)/secretstorage-$(secretstorage-version): \
+                        $(ipydir)/jeepney-$(jeepney-version) \
+                        $(ipydir)/cryptography-$(cryptography-version)
+	tarball=secretstorage-$(secretstorage-version).tar.gz
+	$(call import-source, $(secretstorage-url), $(secretstorage-checksum))
+	$(call pybuild, tar xf, SecretStorage-$(secretstorage-version), , \
 	                SecretStorage $(secretstorage-version))
 
-$(ipydir)/setuptools: $(ibidir)/unzip \
-                      $(ibidir)/python \
-                      $(tdir)/setuptools-$(setuptools-version).zip
-	$(call pybuild, unzip, setuptools-$(setuptools-version), ,\
+$(ipydir)/setuptools-$(setuptools-version): \
+                     $(ibidir)/unzip-$(unzip-version) \
+                     $(ibidir)/python-$(python-version)
+	tarball=setuptools-$(setuptools-version).zip
+	$(call import-source, $(setuptools-url), $(setuptools-checksum))
+	$(call pybuild, unzip, setuptools-$(setuptools-version), , \
 	                Setuptools $(setuptools-version))
 
-$(ipydir)/setuptools_scm: $(ipydir)/setuptools \
-                          $(tdir)/setuptools_scm-$(setuptools_scm-version).tar.gz
-	$(call pybuild, tar xf, setuptools_scm-$(setuptools_scm-version), ,\
+$(ipydir)/setuptools_scm-$(setuptools_scm-version): \
+                         $(ipydir)/setuptools-$(setuptools-version)
+	tarball=setuptools_scm-$(setuptools_scm-version).tar.gz
+	$(call import-source, $(setuptools_scm-url), $(setuptools_scm-checksum))
+	$(call pybuild, tar xf, setuptools_scm-$(setuptools_scm-version), , \
 	                Setuptools-scm $(setuptools_scm-version))
 
-$(ipydir)/sip_tpv: $(ipydir)/sympy \
-                   $(ipydir)/astropy \
-                   $(tdir)/sip_tpv-$(sip_tpv-version).tar.gz
-	$(call pybuild, tar xf, sip_tpv-$(sip_tpv-version), ,) \
-	&& cp $(dtexdir)/sip_tpv.tex $(ictdir)/ \
-	&& echo "sip_tpv $(sip_tpv-version) \citep{sip-tpv}" > $@
+$(ipydir)/sip_tpv-$(sip_tpv-version): \
+                  $(ipydir)/sympy-$(sympy-version) \
+                  $(ipydir)/astropy-$(astropy-version)
+	tarball=sip_tpv-$(sip_tpv-version).tar.gz
+	$(call import-source, $(sip_tpv-url), $(sip_tpv-checksum))
+	$(call pybuild, tar xf, sip_tpv-$(sip_tpv-version), ,)
+	cp $(dtexdir)/sip_tpv.tex $(ictdir)/
+	echo "sip_tpv $(sip_tpv-version) \citep{sip-tpv}" > $@
 
 
-$(ipydir)/six: $(ipydir)/setuptools \
-               $(tdir)/six-$(six-version).tar.gz
-	$(call pybuild, tar xf, six-$(six-version), ,\
+$(ipydir)/six-$(six-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=six-$(six-version).tar.gz
+	$(call import-source, $(six-url), $(six-checksum))
+	$(call pybuild, tar xf, six-$(six-version), , \
 	                Six $(six-version))
 
-$(ipydir)/soupsieve: $(ipydir)/setuptools \
-                     $(tdir)/soupsieve-$(soupsieve-version).tar.gz
-	$(call pybuild, tar xf, soupsieve-$(soupsieve-version), ,\
+$(ipydir)/soupsieve-$(soupsieve-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=soupsieve-$(soupsieve-version).tar.gz
+	$(call import-source, $(soupsieve-url), $(soupsieve-checksum))
+	$(call pybuild, tar xf, soupsieve-$(soupsieve-version), , \
 	                SoupSieve $(soupsieve-version))
 
-$(ipydir)/sympy: $(ipydir)/mpmath \
-                 $(tdir)/sympy-$(sympy-version).tar.gz
-	$(call pybuild, tar xf, sympy-$(sympy-version), ,) \
-	&& cp $(dtexdir)/sympy.tex $(ictdir)/ \
-	&& echo "SymPy $(sympy-version) \citep{sympy}" > $@
-
-$(ipydir)/uncertainties: $(ipydir)/numpy \
-                         $(tdir)/uncertainties-$(uncertainties-version).tar.gz
-	$(call pybuild, tar xf, uncertainties-$(uncertainties-version), ,\
+$(ipydir)/sympy-$(sympy-version): $(ipydir)/mpmath-$(mpmath-version)
+	tarball=sympy-$(sympy-version).tar.gz
+	$(call import-source, $(sympy-url), $(sympy-checksum))
+	$(call pybuild, tar xf, sympy-$(sympy-version), ,)
+	cp $(dtexdir)/sympy.tex $(ictdir)/
+	echo "SymPy $(sympy-version) \citep{sympy}" > $@
+
+$(ipydir)/uncertainties-$(uncertainties-version): $(ipydir)/numpy-$(numpy-version)
+	tarball=uncertainties-$(uncertainties-version).tar.gz
+	$(call import-source, $(uncertainties-url), $(uncertainties-checksum))
+	$(call pybuild, tar xf, uncertainties-$(uncertainties-version), , \
 	                uncertainties $(uncertainties-version))
 
-$(ipydir)/urllib3: $(ipydir)/setuptools \
-                   $(tdir)/urllib3-$(urllib3-version).tar.gz
-	$(call pybuild, tar xf, urllib3-$(urllib3-version), ,\
+$(ipydir)/urllib3-$(urllib3-version): $(ipydir)/setuptools-$(setuptools-version)
+	tarball=urllib3-$(urllib3-version).tar.gz
+	$(call import-source, $(urllib3-url), $(urllib3-checksum))
+	$(call pybuild, tar xf, urllib3-$(urllib3-version), , \
 	                Urllib3 $(urllib3-version))
 
-$(ipydir)/webencodings: $(ipydir)/setuptools \
-                        $(tdir)/webencodings-$(webencodings-version).tar.gz
-	$(call pybuild, tar xf, webencodings-$(webencodings-version), ,\
+$(ipydir)/webencodings-$(webencodings-version): \
+                       $(ipydir)/setuptools-$(setuptools-version)
+	tarball=webencodings-$(webencodings-version).tar.gz
+	$(call import-source, $(webencodings-url), $(webencodings-checksum))
+	$(call pybuild, tar xf, webencodings-$(webencodings-version), , \
 	                Webencodings $(webencodings-version))