cc/gcc: add option for linker hash style

Add an option to specify the hash type that gcc will ask the linker to use.
It is a provision for the upcoming 4.7, as no version currently supports it.

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

 # Compute sparc-specific values

 CT_DoArchTupleValues() {

     # That's the only thing to override

     if [ "${CT_ARCH_64}" = "y" ]; then

         CT_TARGET_ARCH="${CT_ARCH}64"

     fi

 }