cc/gcc: install the core compilers in the build-tools dir

There really is no good reason to install the core compilers in their
own places, one for each pass. We can install them with the other
build tools.

Also, this implies that:
- there are fewer directories to save/restore
- there are fewer symlinks to create for binutils
- the PATH is shorter

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

 # m68k specific configuration file

 ## depends on EXPERIMENTAL

 ##

 ## select ARCH_SUPPORTS_32

 ## select ARCH_DEFAULT_32

 ## select ARCH_DEFAULT_BE

 ## select ARCH_SUPPORTS_WITH_CPU

 ##

 ## help The m68k architecture