xcompile: Detect clang compilers

This uses the availability of CONFIG_* variables in .xcompile and tests for
compilers in xcompile so that the build system doesn't need to probe them.

Change-Id: I359ad6245d2527efa7e848a9b38f5f194744c827
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/10424
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
1 file changed