cc/gcc: add host parameter to core compiler build process

Tell the core compiler what host it should run on (instead of
hard-coding runing on CT_HOST).

No functional change so far, switching between CT_HOST and CT_BUILD
will come in a following patch.

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

 reporter_name="Harold Grovesteen"

 reporter_url="http://sourceware.org/ml/crossgcc/2009-11/msg00052.html"

 reporter_comment=""