cc/gcc: speed up the build a little bit

Even if the current process is highly parallel, crosstool-NG spends most
of its time in single-job steps on fast machines (with a 12-CPU system,
I approximate the parallel vs. non-parallel time to be in the order os
1 to 3; that is crostool-NG spends two-thirds of its time running
non-parallel jobs).

Some steps to build gcc can be paralleled, gaining a litle bit of time
on the whole compilation.

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

 }