image: only define the rules of selected devices

A target defines more than 100 devices, and the image Makefile
expands the kernel, image and artifact rules of every one of them. The
rules of a device that is not selected are only reachable through
install-disabled and compile-disabled, so nothing uses them. The image
Makefile is parsed twice per build, 0.3 s each for mediatek.

Only expand Device/Build for selected devices, and for all devices if
CONFIG_IB is set, as the ImageBuilder compiles them all.

Signed-off-by: John Crispin <john@phrozen.org>

include/image.mk

@@ -966,10 +966,19 @@ define Device
   $(call Device/Default,$(1))
   $(call Device/$(1),$(1))
   $(call Device/Check,$(1))
-  $(call Device/$(if $(DUMP),Dump,Build),$(1))
+  $(if $(DUMP),$(call Device/Dump,$(1)),$(call Device/BuildSelected,$(1)))
 
 endef
 
+# The rules of a device that is not selected can not be reached, and a
+# target defines more than 100 devices, so do not define them. The whole
+# image Makefile is parsed twice per build.
+define Device/BuildSelected
+  ifneq ($(CONFIG_IB)$$(_PROFILE_SET),)
+$(call Device/Build,$(1))
+  endif
+endef
+
 define BuildImage
 
   ifneq ($(DUMP),)