fs/tar: make results reproducible

In order to make tar images reproducible, force files order in tarball.

This work was sponsored by `BA Robotic Systems'.

Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

fs/tar/tar.mk

@@ -7,7 +7,8 @@
 TAR_OPTS := $(call qstrip,$(BR2_TARGET_ROOTFS_TAR_OPTIONS))
 
 define ROOTFS_TAR_CMD
-	tar $(TAR_OPTS) -cf $@ --numeric-owner -C $(TARGET_DIR) .
+	(cd $(TARGET_DIR); find -print0 | LC_ALL=C sort -z | \
+		tar $(TAR_OPTS) -cf $@ --null -T - --no-recursion --numeric-owner)
 endef
 
 $(eval $(call ROOTFS_TARGET,tar))