Fix dependencies around tools/*-event-log-tags.py

We should regenerate merged tag files and java sources when
these scripts are updated.

Change-Id: Id5f11d6f480f3f74dab08f01e929ee2d7fafd2d0
diff --git a/core/java.mk b/core/java.mk
index 6fb16ea..32ec8e4 100644
--- a/core/java.mk
+++ b/core/java.mk
@@ -354,7 +354,8 @@
 logtags_java_sources := $(patsubst %.logtags,%.java,$(addprefix $(intermediates.COMMON)/src/, $(logtags_sources)))
 logtags_sources := $(addprefix $(LOCAL_PATH)/, $(logtags_sources))
 
-$(logtags_java_sources): $(intermediates.COMMON)/src/%.java: $(LOCAL_PATH)/%.logtags $(TARGET_OUT_COMMON_INTERMEDIATES)/all-event-log-tags.txt
+$(logtags_java_sources): PRIVATE_MERGED_TAG := $(TARGET_OUT_COMMON_INTERMEDIATES)/all-event-log-tags.txt
+$(logtags_java_sources): $(intermediates.COMMON)/src/%.java: $(LOCAL_PATH)/%.logtags $(TARGET_OUT_COMMON_INTERMEDIATES)/all-event-log-tags.txt $(JAVATAGS) build/tools/event_log_tags.py
 	$(transform-logtags-to-java)
 
 else