crossgcc: improve error message on missing tools

People were confused about the 'missing toolchain', so
improve the error message.

Change-Id: Icaee338aeedce2255bcfdafe5407c9df02ad9c4a
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/10036
Tested-by: build bot (Jenkins)
Reviewed-by: Idwer Vollering <vidwer@gmail.com>
1 file changed