Add dependency of import_includes on LOCAL_MODULE_MAKEFILE

So the build system regenerates import_includes when you modify
Android.mk to add a new dependency library.

Change-Id: Ic92b097b659bb68a9065e1d66da59e0dc7e2836a
diff --git a/core/binary.mk b/core/binary.mk
index d020846..224f328 100644
--- a/core/binary.mk
+++ b/core/binary.mk
@@ -840,11 +840,12 @@
       $(call intermediates-dir-for,SHARED_LIBRARIES,$(l),$(LOCAL_IS_HOST_MODULE),,$(LOCAL_2ND_ARCH_VAR_PREFIX))/export_includes) \
     $(foreach l, $(my_static_libraries) $(my_whole_static_libraries), \
       $(call intermediates-dir-for,STATIC_LIBRARIES,$(l),$(LOCAL_IS_HOST_MODULE),,$(LOCAL_2ND_ARCH_VAR_PREFIX))/export_includes))
-$(import_includes) : $(import_includes_deps)
+$(import_includes): PRIVATE_IMPORT_EXPORT_INCLUDES := $(import_includes_deps)
+$(import_includes) : $(LOCAL_MODULE_MAKEFILE) $(import_includes_deps)
 	@echo Import includes file: $@
 	$(hide) mkdir -p $(dir $@) && rm -f $@
 ifdef import_includes_deps
-	$(hide) for f in $^; do \
+	$(hide) for f in $(PRIVATE_IMPORT_EXPORT_INCLUDES); do \
 	  cat $$f >> $@; \
 	done
 else