images: append to existing image with ubinize-image build cmd

Let ubinize-image append the ubinized image to the existing image
instead of replacing it.

Fixes: 6c17d71973 ("scripts: ubinize-image.sh: support static volumes, make size optional")
Signed-off-by: Daniel Golle <[email protected]>

include/image-commands.mk

@@ -157,11 +157,13 @@ define Build/ubinize-image
 		$(if $(UBOOTENV_IN_UBI),--uboot-env) \
 		$(foreach part,$(UBINIZE_PARTS),--part $(part)) \
 		--part $(word 1,$(1))="$(BIN_DIR)/$(DEVICE_IMG_PREFIX)-$(word 2,$(1))" \
-		$@ \
+		$@.tmp \
 		-p $(BLOCKSIZE:%k=%KiB) -m $(PAGESIZE) \
 		$(if $(SUBPAGESIZE),-s $(SUBPAGESIZE)) \
 		$(if $(VID_HDR_OFFSET),-O $(VID_HDR_OFFSET)) \
 		$(UBINIZE_OPTS)
+	cat [email protected] >> $@
+	rm [email protected]
 endef
 
 define Build/ubinize-kernel