Makefile: Don't use llvm-mc for the moment

The LLVM integrated assembler has some deficiencies in support for
building AGESA. See:

LLVM PR18918 - [RFE]: Missing altmacro support in integrated assembler

Disable llvm-mc for the moment until these have been addressed fully
upstream.

Change-Id: Id4131d1de04d01c0bec284f976f0ba9662b950ab
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Reviewed-on: http://review.coreboot.org/5711
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
Tested-by: build bot (Jenkins)
1 file changed