cc/gcc: use proper host compiler for canadian bare-metal

While compiling a canadian toolchain for host=mingw32, build=linux,
target=m68k-elf the build fails because in this step of the gcc build
the Host compiler is used in this stage with the build-flags for the
build system. This results in an error where the header <sys/wait.h>
cannot be found.
This problem happens at least in the GCC-4.3.x and GCC-4.4.x range.

This is solved by passing the proper compilers on the Make cmd-line

Signed-off-by: Remy Bohmer <linux@bohmer.net>

hg