image: when using the new image build code, gzip ext4 images by default

This reduces the amount of hacks in the makefile code.

Remove the apm821xx code to do the same - it was broken and left both
compressed and uncompressed images in $(BIN_DIR)

Signed-off-by: Felix Fietkau <nbd@nbd.name>

include/image.mk

@@ -445,7 +445,8 @@ define Device/Build/kernel
 endef
 
 define Device/Build/image
-  $$(_TARGET): $(BIN_DIR)/$(call IMAGE_NAME,$(1),$(2))
+  GZ_SUFFIX := $(if $(filter %dtb %gz,$(2)),,$(if $(and $(findstring ext4,$(1)),$(CONFIG_TARGET_IMAGES_GZIP)),.gz))
+  $$(_TARGET): $(BIN_DIR)/$(call IMAGE_NAME,$(1),$(2))$$(GZ_SUFFIX)
   $(eval $(call Device/Export,$(KDIR)/tmp/$(call IMAGE_NAME,$(1),$(2)),$(1)))
   ROOTFS/$(1)/$(3) := \
 	$(KDIR)/root.$(1)$$(strip \
@@ -462,6 +463,10 @@ define Device/Build/image
 	$$(call concat_cmd,$(if $(IMAGE/$(2)/$(1)),$(IMAGE/$(2)/$(1)),$(IMAGE/$(2))))
 
   .IGNORE: $(BIN_DIR)/$(call IMAGE_NAME,$(1),$(2))
+
+  $(BIN_DIR)/$(call IMAGE_NAME,$(1),$(2)).gz: $(KDIR)/tmp/$(call IMAGE_NAME,$(1),$(2))
+	gzip -c -9n $$^ > $$@
+
   $(BIN_DIR)/$(call IMAGE_NAME,$(1),$(2)): $(KDIR)/tmp/$(call IMAGE_NAME,$(1),$(2))
 	cp $$^ $$@
 

target/linux/apm821xx/image/Makefile

@@ -232,7 +232,6 @@ endef
 
 define Build/hdd-img
 	./mbl_gen_hdd_img.sh $@ $@.boot $(IMAGE_ROOTFS)
-	$(if $(CONFIG_TARGET_IMAGES_GZIP),gzip -9n -c $@ > $(BIN_DIR)/$(notdir $@).gz)
 endef
 
 define Device/MyBookLiveDefault