fs: ensure $(TARGET_DIR_WARNING_FILE) is writable

If the Buildroot tree is read-only, then $(TARGET_DIR_WARNING_FILE) is
copied read-only into target/ but we may want to remove it during the
build process.

This poses no real problem, since target/ itself is guaranteed to be
writable, but for good measure, force $(TARGET_DIR_WARNING_FILE) to be
writable itself.

Reported-by: Danomi Manchego <danomimanchego123@gmail.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

Makefile

@@ -475,7 +475,7 @@ $(BUILD_DIR)/.root:
 	rsync -a $(RSYNC_VCS_EXCLUSIONS) \
 		--chmod=Du+w --exclude .empty --exclude '*~' \
 		$(TARGET_SKELETON)/ $(TARGET_DIR)/
-	cp support/misc/target-dir-warning.txt $(TARGET_DIR_WARNING_FILE)
+	$(INSTALL) -m 0644 support/misc/target-dir-warning.txt $(TARGET_DIR_WARNING_FILE)
 	@ln -snf lib $(TARGET_DIR)/$(LIB_SYMLINK)
 	@mkdir -p $(TARGET_DIR)/usr
 	@ln -snf lib $(TARGET_DIR)/usr/$(LIB_SYMLINK)

fs/common.mk

@@ -83,7 +83,7 @@ endif
 	echo "$$(ROOTFS_$(2)_CMD)" >> $$(FAKEROOT_SCRIPT)
 	chmod a+x $$(FAKEROOT_SCRIPT)
 	$$(HOST_DIR)/usr/bin/fakeroot -- $$(FAKEROOT_SCRIPT)
-	cp support/misc/target-dir-warning.txt $$(TARGET_DIR_WARNING_FILE)
+	$(INSTALL) -m 0644 support/misc/target-dir-warning.txt $$(TARGET_DIR_WARNING_FILE)
 	-@rm -f $$(FAKEROOT_SCRIPT) $$(FULL_DEVICE_TABLE)
 ifneq ($$(ROOTFS_$(2)_COMPRESS_CMD),)
 	$$(ROOTFS_$(2)_COMPRESS_CMD) $$@ > $$@$$(ROOTFS_$(2)_COMPRESS_EXT)