fs/common: lock modification times in $TARGET_DIR

Make sure all files in $TARGET_DIR have a defined modification time
before to generate filesystems.

This work was sponsored by `BA Robotic Systems'.

Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

fs/common.mk

@@ -95,6 +95,9 @@ endif
 	$$(foreach s,$$(call qstrip,$$(BR2_ROOTFS_POST_FAKEROOT_SCRIPT)),\
 		echo "echo '$$(TERM_BOLD)>>>   Executing fakeroot script $$(s)$$(TERM_RESET)'" >> $$(FAKEROOT_SCRIPT); \
 		echo $$(s) $$(TARGET_DIR) $$(BR2_ROOTFS_POST_SCRIPT_ARGS) >> $$(FAKEROOT_SCRIPT)$$(sep))
+ifeq ($$(BR2_REPRODUCIBLE),y)
+	echo "find $$(TARGET_DIR) -print0 | xargs -0 -r touch -hd @$$(SOURCE_DATE_EPOCH)" >> $$(FAKEROOT_SCRIPT)
+endif
 	$$(call PRINTF,$$(ROOTFS_$(2)_CMD)) >> $$(FAKEROOT_SCRIPT)
 	chmod a+x $$(FAKEROOT_SCRIPT)
 	PATH=$$(BR_PATH) $$(HOST_DIR)/usr/bin/pseudo -- $$(FAKEROOT_SCRIPT)