buildsystem: check for coreboot toolchain by default

Other toolchains just don't cut it.

Change-Id: I7a0bdf60d89b5166c9a22c9e9f3f326b28f777b8
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/4584
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

Makefile.inc

@@ -23,6 +23,18 @@ export KERNELVERSION := $(shell if [ -d "$(top)/.git" -a -f "`which git`" ]; \
        then git describe --dirty --always || git describe; \
        else echo 4.0$(KERNELREVISION); fi)
 
+#######################################################################
+# Test for coreboot toolchain (except when explicitely not requested)
+ifneq ($(NOCOMPILE),1)
+# only run if we're doing a build (not for tests, kconfig, ...)
+ifneq ($(CONFIG_ANY_TOOLCHAIN),y)
+_toolchain=$(shell $(CC_i386) -v 2>&1 |grep -q "gcc version .*coreboot toolchain" && echo coreboot)
+ifneq ($(_toolchain),coreboot)
+$(error Please use the coreboot toolchain (or prove that your toolchain works))
+endif
+endif
+endif
+
 #######################################################################
 # Basic component discovery
 MAINBOARDDIR=$(call strip_quotes,$(CONFIG_MAINBOARD_DIR))