build: move append-file to image-commands.mk

Move it append-file to image-commands.mk so that it can used by other
targets as well.

Signed-off-by: Joseph C. Lehner <joseph.c.lehner@gmail.com>

include/image-commands.mk

@@ -110,6 +110,10 @@ define Build/append-rootfs
 	dd if=$(IMAGE_ROOTFS) >> $@
 endef
 
+define Build/append-file
+	cat "$(1)" >> "$@"
+endef
+
 define Build/append-ubi
 	sh $(TOPDIR)/scripts/ubinize-image.sh \
 		$(if $(UBOOTENV_IN_UBI),--uboot-env) \

target/linux/ipq806x/image/Makefile

@@ -31,10 +31,6 @@ define Image/Build
 	dd if=$(KDIR)/root.$(1) of=$(BIN_DIR)/$(IMG_PREFIX)-$(1)-root.img bs=2k conv=sync
 endef
 
-define Build/append-file
-	cat $(1) >> $@
-endef
-
 define Device/Default
 	PROFILES := Default
 	KERNEL_DEPENDS = $$(wildcard $(DTS_DIR)/$$(DEVICE_DTS).dts)