cc/gcc: build lto-plugin if binutils' gold is built

To properly enable LTO with gold, gcc has to install a plugin that gold
uses to handle the LTO information.

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

 # Compute M68k-specific values

 CT_DoArchTupleValues() {

     :

 }