Add proper deps for jarjar rules files.

Changes to the jarjar rules file for a module were not causing
rebuilds; add the missing dependency.

Change-Id: Ib78fa708681cbc414218fe84cc2c4282c619f45f
diff --git a/core/java.mk b/core/java.mk
index f43bf3b..5315ccc 100644
--- a/core/java.mk
+++ b/core/java.mk
@@ -348,7 +348,7 @@
 # Run jarjar if necessary, otherwise just copy the file.
 ifneq ($(strip $(LOCAL_JARJAR_RULES)),)
 $(full_classes_jarjar_jar): PRIVATE_JARJAR_RULES := $(LOCAL_JARJAR_RULES)
-$(full_classes_jarjar_jar): $(full_classes_compiled_jar) | $(JARJAR)
+$(full_classes_jarjar_jar): $(full_classes_compiled_jar) $(LOCAL_JARJAR_RULES) | $(JARJAR)
 	@echo JarJar: $@
 	$(hide) java -jar $(JARJAR) process $(PRIVATE_JARJAR_RULES) $< $@
 else