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>

 #!/bin/sh

 call_to=@@DEFAULT_LD@@

 case "${CTNG_LD_IS}" in

     bfd)    call_to=bfd;;

     gold)   call_to=gold;;

 esac

 exec "${0}.${call_to}" "$@"

 exit $?