Fix environment variables when building file list for core updates

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

src/scripts/archive.files

@@ -19,6 +19,13 @@
 #                                                                             #
 ###############################################################################
 
+for i in BUILD_ARCH BUILDTARGET KVER; do
+	if [ -z "${!i}" ]; then
+		echo "${i} not set" >&2
+		exit 1
+	fi
+done
+
 FILELIST=
 
 for dir in $@; do