GCC fails post-install step when build without fortran

[bertwesarg]

Building (any) GCC EB without fortran (--try-amend=languages=c,c++) fails the post-install step because it unconditionally try to create an f77 symlink to gfortran, which does not exist.

== 2024-05-02 14:56:48,215 build_log.py:171 ERROR EasyBuild crashed with an error (at easybuild/software/EasyBuild/4.9.1/lib/python3.11/site-packages/easybuild/tools/build_log.py:111 in caller_info): Build of /tmp/eb-w9i60165/tweaked_easyconfigs/GCCcore-13.2.0.eb failed (err: "build failed (first 300 chars): Can't link '/home/build/.local/easybuild/software/GCCcore/13.2.0/bin/f77' to non-existing location /home/build/.local/easybuild/software/GCCcore/13.2.0/bin/gfortran") (at easybuild/software/EasyBuild/4.9.1/lib/python3.11/site-packages/easybuild/main.py:176 in build_and_install_software)
ERROR: Build of /tmp/eb-w9i60165/tweaked_easyconfigs/GCCcore-13.2.0.eb failed (err: "build failed (first 300 chars): Can't link '/home/build/.local/easybuild/software/GCCcore/13.2.0/bin/f77' to non-existing location /home/build/.local/easybuild/software/GCCcore/13.2.0/bin/gfortran")

$ eb GCCcore-13.2.0.eb -l --robot --try-amend=languages=c,c++