Kconfig: add comments for toolchain choices

- While we're working on fixing clang for coreboot, mark it as not
currently working so that it doesn't look like a reasonable choice.

- Add help on how to make the toolchains

Change-Id: Ib37093ca98d0328fad40dd7886c98d00f78bd58e
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/13053
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

0 files changed, 0 insertions, 0 deletions