binutils/binutils: add wrapper to gold and ld

When both gold and ld are installed, add a wrapper that calls
to either gold or ld.

In case the wrapper is installed, we also need to symlink ld.bfd
and ld.gold for the core_cc steps.

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 $?