binutils: introduce the infrastructure to support binutils alternatives

Rework binutils in order to provide soon binutils alternative.

Signed-off-by: Yann Diorcet <diorcet.yann@gmail.com>
[yann.morin.1998@free.fr: split up original patch for self-contained changes]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Message-Id: <d3d1d51f399e6d2c1163.1353320546@macbook-smorlat.local>
Patchwork-Id: 199971

# Compute s390-specific values

CT_DoArchTupleValues() {

    # That's the only thing to override

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

        CT_TARGET_ARCH="s390x"

    fi

}