binutils/binutils: add blind option to force use of ld.bfd during build

gold is not capable of building glibc/eglibc, so we have to
force using the BFD linker, ld.bfd.

Offer a blind option that affected components can select to
force use of the BFD linker during the build.

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

 # Compute Alpha-specific values

 CT_DoArchTupleValues () {

     # The architecture part of the tuple:

     CT_TARGET_ARCH="${CT_ARCH}${CT_ARCH_ALPHA_VARIANT}"

 }