cc/gcc: frontends are responsible for selecting the list of languages

Do for the final step the same as for the core step: compute the list
of selected langauages from the frontend, not in the backend.

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

# Compute sparc-specific values

CT_DoArchTupleValues() {

    # That's the only thing to override

    if [ "${CT_ARCH_64}" = "y" ]; then

        CT_TARGET_ARCH="${CT_ARCH}64"

    fi

}