build: set LC_ALL=C

Avoids tools such as layoutrom stumble over localized messages.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Tested-By: Patrick Georgi <pgeorgi@google.com>
diff --git a/Makefile b/Makefile
index eecb8a1..1cff1d0 100644
--- a/Makefile
+++ b/Makefile
@@ -12,6 +12,7 @@
 export CONFIG_SHELL       := sh
 export KCONFIG_AUTOHEADER := autoconf.h
 export KCONFIG_CONFIG     := $(CURDIR)/.config
+export LC_ALL             := C
 CROSS_PREFIX=
 ifneq ($(CROSS_PREFIX),)
 CC=$(CROSS_PREFIX)gcc