libc/glibc-common: force use of the BFD linker

gold can not build glibc/eglibc, force use of the BFD
linker during the toolchain build.

Reported-by: Bill Pringlemeir <bpringle@sympatico.ca>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 reporter_name="Remy Bohmer"

 reporter_url="linux@bohmer.net"

 reporter_comment="Example for building a toolchain for m68000 bare metal targets"