Better configure checks to see if GCC can be built

Until now, to test if GCC can use `sys/cdefs.h', we were building
a small test program using it. But after testing on an Ubuntu 14.04,
we noticed that the GCC test during the configure script passes, but
GCC still can't be built. After some investigation we noticed its
available in other directories, but during the build of GCC, those
directories aren't used, and it only assumes it to be under
`/usr/include'. So with this commit, we are only checking this
particular location for this header, not a test run of GCC.

After fixing this, we noticed that GCC's build crashed again because
it couldn't link with `libc.a' (or `libc.so'). So we also added a
for this library and added a new warning to inform the user what they
might be able to do.

Finally, we noticed that in one of the last steps of building GCC,
we weren't using `&&', but `;', so the GCC name file would be
built, even when the GCC build failed.

2 files changed, 64 insertions, 26 deletions

diff --git a/configure b/configure
index a71c815..0c0404d 100755
--- a/configure
+++ b/configure
@@ -884,42 +884,80 @@ fi
 #
 # 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.
+# `/usr/include/sys/cdefs.h' and `/usr/lib/libc.a' are not available by
+# default. So GCC will crash with different ugly errors! The only solution
+# is that user manually installs the `multilib' part as root, before
+# running the configure script.
+#
+# Note that `sys/cdefs.h' may be available in other directories (for
+# example `/usr/include/x86_64-linux-gnu/') that are automatically included
+# in an installed GCC. HOWEVER during the build of GCC, all those other
+# directories are ignored. So even if they exist, they are useless.
+warningsleep=0
 if [ $host_cc = 0 ]; then
-    tfile=$sdir/gcc-cdefs-test.c;
-    echo "#include <sys/cdefs.h>"     > $tfile;
-    echo "int main(void){return 0;}" >> $tfile;
-    if gcc $tfile -o $sdir/gcc-cdefs-test &> /dev/null; then
-        rm $sdir/gcc-cdefs-test*;
-    else
+    if ! [ -f /usr/include/sys/cdefs.h ]; then
         host_cc=1
-    fi;
-    rm -f $tfile;
+        warningsleep=1
+        cat <<EOF
+
+!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+!!!!!!!!!!!!!!!!!!!!!!         Warning        !!!!!!!!!!!!!!!!!!!!!!
+!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+This system doesn't have '/usr/include/sys/cdefs.h'. Because of this, the
+project can't build its custom GCC to ensure better reproducibility. We
+strongly recommend installing the proper package (for your operating
+system) that installs this necessary file. For example on some Debian-based
+GNU/Linux distros, you need these two packages: 'gcc-multilib' and
+'g++-multilib'.
+!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+EOF
+    fi
 
-    if [ $host_cc = 1 ]; then
+    if [ -f /usr/lib/libc.a ] || [ -f /usr/lib64/libc.a ]; then
+        # This is just a place holder
+        host_cc=$host_cc
+    else
+        host_cc=1
+        warningsleep=1
         cat <<EOF
 
 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 !!!!!!!!!!!!!!!!!!!!!!         Warning        !!!!!!!!!!!!!!!!!!!!!!
 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
-This system's C compiler (called with 'gcc') can't include
-'sys/cdefs.h. Because of this, the project can't build its custom GCC to
-ensure better reproducibility. We strongly recommend installing the proper
-package (for your operating system) that installs this necessary 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(s) to
-complete your C compiler, then re-run './configure'.
+This system doesn't have '/usr/lib/libc.a' or '/usr/lib64/libc.a'. Because
+of this, the project can't build its custom GCC to ensure better
+reproducibility. We strongly recommend installing the proper package (for
+your operating system) that installs this necessary file.
+
+Some possible solutions:
+  1. On some Debian-based GNU/Linux distros, these two packages may fix the
+     problem: 'gcc-multilib' and 'g++-multilib'.
+  2. (BE CAREFUL!) If you have '/usr/lib/x86_64-linux-gnu' but don't have
+     '/usr/lib64', then running the following command might fix this
+     particular problem by making a symbolic link.
+         $ sudo ln -s /usr/lib/x86_64-linux-gnu /usr/lib64
+     After the configure script is finished, delete the link with 'rm
+     /usr/lib64' (you won't need it any more as far as this project is
+     concerned).
 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
 EOF
+    fi
+
+    if [ $warningsleep = 1 ]; then
+        cat <<EOF
+
+PLEASE SEE THE WARNINGS ABOVE.
+
+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(s) to complete your C
+compiler, then re-run './configure'.
+
+EOF
         sleep 5
     fi
 fi
diff --git a/reproduce/software/make/basic.mk b/reproduce/software/make/basic.mk
index 6704993..abcd5a9 100644
--- a/reproduce/software/make/basic.mk
+++ b/reproduce/software/make/basic.mk
@@ -1057,7 +1057,7 @@ $(ibidir)/gcc: $(gcc-prerequisites)   \
 	           patchelf --set-rpath $(ildir) $$f;                      \
 	         fi;                                                       \
 	       done;                                                       \
-	     fi;                                                           \
-	  ln -sf $(ibdir)/gcc $(ibdir)/cc                                  \
+	     fi                                                            \
+	  && ln -sf $(ibdir)/gcc $(ibdir)/cc                               \
 	  && echo "GNU Compiler Collection (GCC) $(gcc-version)" > $@;     \
 	fi