binutils/binutils: hide gold option if no support for current architecture

The gold linker does currently support only a limited set of architectures:
- x86 (32- and 64-bit)
- ARM

Hide the gold option for other architectures.

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

 reporter_name="Nye Liu"

 reporter_url="http://sourceware.org/ml/crossgcc/2008-10/msg00046.html"

 reporter_comment=""