Fix build by adding @Override

Change-Id: Iccdd4e1a34aff098d640204f599979012e671b0d
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/enums/EnumUnboxer.java b/src/main/java/com/android/tools/r8/ir/optimize/enums/EnumUnboxer.java
index 43c57fc..d99d342 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/enums/EnumUnboxer.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/enums/EnumUnboxer.java
@@ -662,6 +662,7 @@
             to, RewrittenPrototypeDescription.createForRewrittenTypes(returnInfo, builder.build()));
       }
 
+      @Override
       public GraphLense build(DexItemFactory dexItemFactory, GraphLense previousLense) {
         if (typeMap.isEmpty() && methodMap.isEmpty() && fieldMap.isEmpty()) {
           return previousLense;