Hello everyone

This is a follow up to better explain what the problem is with the
sans-libc cross gcc in the (gnu packages cross-base) module.

In the latest master if you try to build gcc-cross-sans-libc with:

./pre-inst-env guix build -e '((@@(gnu packages cross-base) cross-gcc)
"i686-linux-gnu")' -c8

gcc modules libitm, libvtv and libsanitizer fail to build with
"configure: error: C compiler cannot create executables".

This happens because there is no libc present at that point and the
problem was introduced with commit ca7ef4d41854218c which enabled c++.

At that stage no linking can happen so the best solution is to just
disable the modules. It does not affect anything after that.

I am attaching the build.log so anybody can see for himself. :-)

If okay I will push the patch to master.

Manolis