cc/gcc: rename the core backend function

Rename the core backend function to do_cc_core_backend, to
make it explicit it is a backend.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 #!/bin/sh

 set -e

 printf "Running autoconf...\n"

 autoconf -Wall --force

 printf "Done. You may now run:\n    ./configure\n"