Fix scripts/set-release-date when LC_TIME is set

We actually need to override LC_TIME if it is set, so use LC_ALL which
overrides everything rather than LANG that is used as a fallback.

scripts/set-release-date

@@ -2,7 +2,7 @@
 
 set -e
 
-export LANG=C
+export LC_ALL=C
 
 DATE=${1:-now}