genbuild_h: set LC_ALL=C to get rid of language influence to date

Change-Id: Ia0af9e332522a640dd9aaa3a62d39d691fcfa959
Signed-off-by: Alexander Couzens <lynxis@fe80.eu>
Reviewed-on: http://review.coreboot.org/10449
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

util/genbuild_h/genbuild_h.sh

@@ -23,6 +23,7 @@ GITREV=""
 TIMESOURCE=""
 
 export LANG=C
+export LC_ALL=C
 export TZ=UTC
 
 if [ -d "${top}/.git" ] && [ -f "$(command -v git)" ]; then