cc/gcc: add build frontend

Bizarrely enough, the core gcc are not enough to be able to build a
canadian cross, and a real, full cross compiler is required so that
the canadian cross can be properly built... WTF?!? Sigh...

Add a build-frontend, as was done for the binutils and the complibs.

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

 # Super-H specific configuration file

 ## select ARCH_SUPPORTS_32

 ## select ARCH_DEFAULT_32

 ## select ARCH_USE_MMU

 ## select ARCH_SUPPORTS_BOTH_ENDIAN

 ## select ARCH_DEFAULT_LE

 ##

 ## help The Super-H architecture, as defined by:

 ## help     http://www.renesas.com/fmwk.jsp?cnt=superh_family_landing.jsp&fp=/products/mpumcu/superh_family/