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>

 # x86 specific options

 ## select ARCH_SUPPORTS_32

 ## select ARCH_SUPPORTS_64

 ## select ARCH_DEFAULT_32

 ## select ARCH_USE_MMU

 ## select ARCH_SUPPORT_ARCH

 ## select ARCH_SUPPORT_CPU

 ## select ARCH_SUPPORT_TUNE

 ##

 ## help The x86 architecture, as defined by:

 ## help     32-bit (ia32) : http://www.intel.com/

 ## help     64-bit (amd64): http://www.amd.com/us-en/Processors/DevelopWithAMD/0,,30_2252_875_7044,00.html