kconfig: enforce stable sort order

Locales differ in the order in which they sort entries. This ensures
predictable behavior.

Change-Id: I4ceec90a56bbc368a847d14298db0a21cc21e77c
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Reviewed-on: http://review.coreboot.org/10510
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Alexander Couzens <lynxis@fe80.eu>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
diff --git a/util/kconfig/Makefile b/util/kconfig/Makefile
index a216fd3..f80d531 100644
--- a/util/kconfig/Makefile
+++ b/util/kconfig/Makefile
@@ -2,6 +2,9 @@
 # Kernel configuration targets
 # These targets are used from top-level makefile
 
+export LC_ALL=C
+export LANG=C
+
 PHONY += oldconfig xconfig gconfig menuconfig config silentoldconfig update-po-config \
 	localmodconfig localyesconfig