Revert "Remove unassigned event log tags feature"

Revert submission 3400623-remove_unassigned_event_log_tags

Reason for revert: Droidmonitor created revert due to b/383362497. Will be verifying through ABTD before submission.

Reverted changes: /q/submissionid:3400623-remove_unassigned_event_log_tags

Change-Id: I2f65b8327c1fc43f248685d8fe83bcb94f8e4bf4
diff --git a/core/java.mk b/core/java.mk
index 35026db..5fbc916 100644
--- a/core/java.mk
+++ b/core/java.mk
@@ -140,6 +140,7 @@
 logtags_java_sources := $(patsubst %.logtags,%.java,$(addprefix $(intermediates.COMMON)/logtags/, $(logtags_sources)))
 logtags_sources := $(addprefix $(LOCAL_PATH)/, $(logtags_sources))
 
+$(logtags_java_sources): PRIVATE_MERGED_TAG := $(TARGET_OUT_COMMON_INTERMEDIATES)/all-event-log-tags.txt
 $(logtags_java_sources): $(intermediates.COMMON)/logtags/%.java: $(LOCAL_PATH)/%.logtags $(TARGET_OUT_COMMON_INTERMEDIATES)/all-event-log-tags.txt $(JAVATAGS) build/make/tools/event_log_tags.py
 	$(transform-logtags-to-java)