m68k-linux-gnu-coldfire-soft GCC and glibc often won't build due to
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103370
which results in build-many-glibcs.py failure. Add an option, --exclude,
to exclude some targets.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Sam James <sam@gentoo.org>