build: add mkrasimage

The current make-ras.sh image generation script for the ZyXEL NBG6617
has portability issues with bash. Because of this, factory images are
currently not built correctly by the OpenWRT buildbots.

This commit replaces the make-ras.sh by C-written mkrasimage.

The new mkrasimage is also compatible with other ZyXEL devices using
the ras image-format.
This is not tested with the NBG6616 but it correctly builds the
header for ZyXEL factory image.

Signed-off-by: David Bauer <mail@david-bauer.net>

include/image-commands.mk

@@ -49,17 +49,17 @@ define Build/eva-image
 	mv $@.new $@
 endef
 
-define Build/make-ras
+define Build/zyxel-ras-image
 	let \
 		newsize="$(subst k,* 1024,$(RAS_ROOTFS_SIZE))"; \
-		$(TOPDIR)/scripts/make-ras.sh \
-			--board $(RAS_BOARD) \
-			--version $(RAS_VERSION) \
-			--kernel $(call param_get_default,kernel,$(1),$(IMAGE_KERNEL)) \
-			--rootfs $@ \
-			--rootfssize $$newsize \
-			$@.new
-	@mv $@.new $@
+		$(STAGING_DIR_HOST)/bin/mkrasimage \
+			-b $(RAS_BOARD) \
+			-v $(RAS_VERSION) \
+			-r $@ \
+			-s $$newsize \
+			-o $@.new \
+			$(if $(findstring separate-kernel,$(word 1,$(1))),-k $(IMAGE_KERNEL)) \
+		&& mv $@.new $@
 endef
 
 define Build/mkbuffaloimg