Reinforce the dependency on package-export.apk.

This fixes the bug that if an app has no resource at all, we should
still set up the dependency on package-export.apk, because the
AndroidManifest.xml may still reference symbols in package-export.apk.

Change-Id: Idb3f12abf55c04824da5b666fe7c49694e227e2c
diff --git a/core/package_internal.mk b/core/package_internal.mk
index d2681e5..ce9d67d 100644
--- a/core/package_internal.mk
+++ b/core/package_internal.mk
@@ -297,7 +297,7 @@
     $(foreach lib,$(LOCAL_RES_LIBRARIES),\
         $(call intermediates-dir-for,APPS,$(lib),,COMMON)/src/R.stamp)
 
-$(resource_export_package) $(R_file_stamp): $(all_library_res_package_export_deps)
+$(resource_export_package) $(R_file_stamp) $(LOCAL_BUILT_MODULE): $(all_library_res_package_export_deps)
 $(LOCAL_INTERMEDIATE_TARGETS): \
     PRIVATE_AAPT_INCLUDES := $(all_library_res_package_exports)
 endif # LOCAL_NO_STANDARD_LIBRARIES