image.mk: do not emit multiple target definitions for kernel images

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

SVN-Revision: 45498

include/image.mk

@@ -380,8 +380,8 @@ define Device/Build/check_size
 endef
 
 define Device/Build/kernel
+  _KERNEL_IMAGES += $(KDIR)/$$(KERNEL_NAME)
   $(KDIR)/$$(KERNEL_NAME): image_prepare
-	touch $$@
   $$(_TARGET): $$(if $$(KERNEL_INSTALL),$(BIN_DIR)/$$(KERNEL_IMAGE))
   $(BIN_DIR)/$$(KERNEL_IMAGE): $(KDIR)/$$(KERNEL_IMAGE)
 	cp $$^ $$@
@@ -456,6 +456,9 @@ define BuildImage
   $(foreach device,$(TARGET_DEVICES),$(call Device,$(device)))
   $(foreach fs,$(TARGET_FILESYSTEMS) $(fs-subtypes-y),$(call BuildImage/mkfs,$(fs)))
 
+  $$(sort $$(_KERNEL_IMAGES)):
+	@touch $$@
+
   install: kernel_prepare
 	$(foreach fs,$(TARGET_FILESYSTEMS),
 		$(call Image/Build,$(fs))