Makefile.inc: Make clang once again a valid toolchain

'prove' that clang is supported (to some extent).

Change-Id: I181f4910ba64ab9746e7ac94aa79da23cdd41dad
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/5709
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
Tested-by: build bot (Jenkins)
1 file changed