binutils/binutils: do not forget to extract elf2flt

In case we're using a custom (aka local) binutils source, we still
need to extract and patch elf2flt.

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

# Compute s390-specific values

CT_DoArchTupleValues() {

    # That's the only thing to override

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

        CT_TARGET_ARCH="s390x${CT_ARCH_SUFFIX}"

    fi

}