Avoid extra rdeps copy when finishing node

Reduces garbage and wasted work

--
MOS_MIGRATED_REVID=108566164
diff --git a/src/main/java/com/google/devtools/build/skyframe/BuildingState.java b/src/main/java/com/google/devtools/build/skyframe/BuildingState.java
index ad16c38..ae38e8c 100644
--- a/src/main/java/com/google/devtools/build/skyframe/BuildingState.java
+++ b/src/main/java/com/google/devtools/build/skyframe/BuildingState.java
@@ -153,6 +153,12 @@
         List<Object> getDataToConsolidate(BuildingState container) {
           return container.reverseDepsDataToConsolidate;
         }
+
+        @Override
+        public void consolidateReverseDeps(BuildingState container) {
+          // #consolidateReverseDeps is only supported for node entries, not building states.
+          throw new UnsupportedOperationException();
+        }
       };
 
   // Below are fields that are used for dirty nodes.