cc/gcc: simplify calls to core backend

The core backend is going to have more parameters in the upcoming
patches, so it will be a bit complex to handle.

Introduce an array-variable that is filled by the different code-paths
with the required values.

This makes the code easier to read and maintain.

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"