image: strip metadata from images when used in other artifacts

Image metadata and signature is of no use for images which are included
inside other artifacts (like an SD-card image). Strip them off before
using images in artifacts or stashing them for the ImageBuilder as the
contained signature breaks reproducibility.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
(cherry picked from commit 7a256d9)

include/image-commands.mk

@@ -37,7 +37,11 @@ define Build/package-kernel-ubifs
 endef
 
 define Build/append-image
-	dd if=$(BIN_DIR)/$(DEVICE_IMG_PREFIX)-$(1) >> $@
+	cp "$(BIN_DIR)/$(DEVICE_IMG_PREFIX)-$(1)" "$@.stripmeta"
+	fwtool -s /dev/null -t "$@.stripmeta" || :
+	fwtool -i /dev/null -t "$@.stripmeta" || :
+	dd if="$@.stripmeta" >> "$@"
+	rm "$@.stripmeta"
 endef
 
 ifdef IB
@@ -46,8 +50,12 @@ define Build/append-image-stage
 endef
 else
 define Build/append-image-stage
-	dd if=$(BIN_DIR)/$(DEVICE_IMG_PREFIX)-$(1) of=$(STAGING_DIR_IMAGE)/$(BOARD)$(if $(SUBTARGET),-$(SUBTARGET))-$(DEVICE_NAME)-$(1)
-	dd if=$(BIN_DIR)/$(DEVICE_IMG_PREFIX)-$(1) >> $@
+	cp "$(BIN_DIR)/$(DEVICE_IMG_PREFIX)-$(1)" "$@.stripmeta"
+	fwtool -s /dev/null -t "$@.stripmeta" || :
+	fwtool -i /dev/null -t "$@.stripmeta" || :
+	dd if="$@.stripmeta" of="$(STAGING_DIR_IMAGE)/$(BOARD)$(if $(SUBTARGET),-$(SUBTARGET))-$(DEVICE_NAME)-$(1)"
+	dd if="$@.stripmeta" >> "$@"
+	rm "$@.stripmeta"
 endef
 endif