--host-cc configure option to avoid building GCC, M4 mandatory

In some cases (specially when debugging the pipeline), its very
time-consuming to install GCC. With this commit, a `--host-cc' option has
been added to avoid building the C compiler when necessary.

The test to see if `sys/cdefs.h' is available on the system (necessary to
build GCC) has also been moved to the configure script to print a more
visible warning and also use the new `host_cc' variable to let
`dependencies-basic.mk' know that GCC shouldn't be built.

Finally, we are having problems installing M4 from source, so it has been
set as a mandatory dependency.

2 files changed, 73 insertions, 36 deletions

diff --git a/configure b/configure
index 6f4895b..6059c0e 100755
--- a/configure
+++ b/configure
@@ -35,6 +35,7 @@ set -e
 jobs=0
 build_dir=
 input_dir=
+host_cc=0
 software_dir=
 existing_conf=0
 minmapsize=10000000000
@@ -79,6 +80,7 @@ Configure options:
   -s, --software-dir=STR  Directory containing necessary software tarballs.
 
  Operating mode options:
+      --host-cc           Use host system's C compiler, don't build GCC.
   -m, --minmapsize=INT    (Gnuastro) Minimum number of bytes to use RAM.
   -j, --jobs=INT          Number of threads to build the software.
   -e, --existing-conf     Use (possibly existing) local configuration.
@@ -148,6 +150,8 @@ do
   -m*)                   minmapsize=$(echo   "$1" | sed -e's/-m//'); check_v "$1" "$minmapsize";   shift;;
 
   # Operating mode options
+  --host-cc)              host_cc=1;                                                shift;;
+  --host-cc=*)            on_off_option_error --host-cc;;
   -j|--jobs)              jobs="$2";                          check_v "$1" "$jobs"; shift;shift;;
   -j=*|--jobs=*)          jobs="${1#*=}";                     check_v "$1" "$jobs"; shift;;
   -j*)                    jobs=$(echo "$1" | sed -e's/-j//'); check_v "$1" "$jobs"; shift;;
@@ -800,7 +804,12 @@ fi
 # For the time being, we'll use the existance of `otool' to see if we are
 # on a Mac OS system or not. Some tools (for example OpenSSL) need to know
 # this.
+#
+# On Mac OS, the building of GCC crashes sometimes while building libiberty
+# with CLang's `g++'. Until we find a solution, we'll just use the host's C
+# compiler.
 if type otool > /dev/null 2>/dev/null; then
+    host_cc=1
     on_mac_os=yes
 else
     on_mac_os=no
@@ -865,6 +874,53 @@ fi
 
 
 
+# See if GCC can be built
+# -----------------------
+#
+# On some GNU/Linux distros, the C compiler is broken into `multilib' (for
+# 32-bit and 64-bit support, with their own headers). On these systems,
+# `sys/cdefs.h' is not available by default. So if the user hasn't manually
+# installed it before this configure script, GCC won't build. We are thus
+# explicitly testing a small C program here to see if the host's C compiler
+# won't have any problems in building GCC.
+if [ $host_cc = 0 ]; then
+    tfile=$bdir/gcc-cdefs-test.c;
+    echo "#include <sys/cdefs.h>"     > $$tfile;
+    echo "int main(void){return 0;}" >> $$tfile;
+    if gcc $$tfile -o $bdir/gcc-cdefs-test &> /dev/null; then
+        rm $bdir/gcc-cdefs-test*;
+    else
+        host_cc=1
+    fi;
+    rm $$tfile;
+
+    if [ $host_cc = 1 ]; then
+        cat <<EOF
+
+!!!!!!!!!!!!!!!!!!!!!!!!
+WARNING: Can't build GCC
+!!!!!!!!!!!!!!!!!!!!!!!!
+
+This system's C compiler (called with 'gcc') can't include
+'sys/cdefs.h. Because of this, we can't build our custom GCC. We strongly
+recommend installing the proper package (for your operating system) that
+installs this header file. For example on some Debian-based GNU/Linux
+distros, you need these two packages: 'gcc-multilib' and 'g++-multilib'.
+
+However, since GCC is pretty low-level, this configuration script will
+continue in 5 seconds and use your system's C compiler (it won't build a
+custom GCC). But please consider installing the necessary package to
+complete your C compiler, then re-run the pipeline.
+
+EOF
+        sleep 5
+    fi
+fi
+
+
+
+
+
 # Build Basic dependencies
 # ------------------------
 #
@@ -890,6 +946,7 @@ make -f reproduce/src/make/dependencies-basic.mk \
      needs_ldl=$needs_ldl                        \
      on_mac_os=$on_mac_os                        \
      numthreads=$numthreads                      \
+     host_cc=$host_cc                            \
      -j$numthreads
 
 
diff --git a/reproduce/src/make/dependencies-basic.mk b/reproduce/src/make/dependencies-basic.mk
index f7f83ed..0f86d95 100644
--- a/reproduce/src/make/dependencies-basic.mk
+++ b/reproduce/src/make/dependencies-basic.mk
@@ -210,8 +210,15 @@ makelink = origpath="$$PATH";                                      \
 	                       | tr '\n' :);                           \
 	   a=$$(which $(1) 2> /dev/null);                              \
 	   if [ -e $(ibdir)/$(1) ]; then rm $(ibdir)/$(1); fi;         \
-	   if [ x"$(2)" = xcopy ]; then c=cp; else c="ln -s"; fi;      \
-	   if [ x$$a != x ]; then $$c $$a $(ibdir)/$(1); fi;           \
+	   if [ x$$a = x ]; then                                       \
+	     if [ "x$(strip $(2))" = xmandatory ]; then                \
+	       echo "'$(1)' is necessary for higher-level tools.";     \
+	       echo "Please install it for the pipeline to continue."; \
+	       exit 1;                                                 \
+	     fi;                                                       \
+	   else                                                        \
+	     ln -s $$a $(ibdir)/$(1);                                  \
+	   fi;                                                         \
 	   export PATH="$$origpath"
 $(ibdir) $(ildir):; mkdir $@
 $(ibidir)/low-level-links: | $(ibdir) $(ildir)
@@ -246,7 +253,7 @@ $(ibidir)/low-level-links: | $(ibdir) $(ildir)
 	$(call makelink,msgfmt)
 
         # GNU M4 (for managing building macros)
-	$(call makelink,m4)
+	$(call makelink,m4,mandatory)
 
         # Needed by TeXLive specifically.
 	$(call makelink,perl)
@@ -767,7 +774,7 @@ $(ibidir)/binutils: $(tdir)/binutils-$(binutils-version).tar.lz
 #
 # We are currently having problems installing GCC on macOS, so for the time
 # being, if the pipeline is being run on a macOS, we'll just set a link.
-ifeq ($(on_mac_os),yes)
+ifeq ($(host_cc),1)
 gcc-prerequisites =
 else
 gcc-prerequisites = $(tdir)/gcc-$(gcc-version).tar.xz \
@@ -784,44 +791,17 @@ $(ibidir)/gcc: $(gcc-prerequisites)   \
                $(ibidir)/diffutils    \
                $(ibidir)/coreutils
 
-        # On a macOS, we (currently!) won't build GCC because of some
-        # errors we are still trying to find. So, we'll just make a
-        # symbolic link to the host's executables.
-        #
         # GCC builds is own libraries in '$(idir)/lib64'. But all other
         # libraries are in '$(idir)/lib'. Since this pipeline 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 '$(idir)/lib'.
-        #
-        # Cases were we currently don't build GCC:
-        #
-        # 1) MacOS: because it crashes sometimes while building libiberty
-        #    with g++.
-        #
-        # 2) GNU/Linux distros that have `multilib' compilers (for 32-bit
-        #    and 64-bit support) need to install a special package to have
-        #    `/usr/include/sys/cdefs.h'. So we are explicitly testing a
-        #    small C program to see if GCC can import it successfully.
-	if [ "x$(on_mac_os)" = xyes ]; then                                \
-	  build=no;                                                        \
-	else                                                               \
-	  tfile=$(ddir)/gcc-cdefs-test.c;                                  \
-	  echo "#include <sys/cdefs.h>"     > $$tfile;                     \
-	  echo "int main(void){return 0;}" >> $$tfile;                     \
-	  if gcc $$tfile &> /dev/null; then                                \
-	       build=yes; rm a.out;                                        \
-	  else build=no;                                                   \
-	  fi;                                                              \
-	  rm $$tfile;                                                      \
-	fi;                                                                \
-                                                                           \
-	if [ $$build = no ]; then                                          \
-	  $(call makelink,g++);                                            \
+	if [ $(host_cc) = 1 ]; then                                        \
 	  $(call makelink,gcc);                                            \
-	  $(call makelink,gfortran);                                       \
-	  ccinfo=$$(gcc --version | awk 'NR==1');             \
-	  echo "C compiler (""$$ccinfo"")" > $@; exit 1;                   \
+	  $(call makelink,g++,mandatory);                                  \
+	  $(call makelink,gfortran,mandatory);                             \
+	  ccinfo=$$(gcc --version | awk 'NR==1');                          \
+	  echo "C compiler (""$$ccinfo"")" > $@;                           \
 	else                                                               \
 	  rm -f $(ibdir)/gcc* $(ibdir)/g++ $(ibdir)/gfortran $(ibdir)/gcov*;\
 	  rm -rf $(ildir)/gcc $(ildir)/libcc* $(ildir)/libgcc*;            \