Add missing OVERRIDE qualifiers in code generators.

Test: mmma art
Change-Id: I91d0a2dc23dc8d63a9bb3607eb1c1517eabaeb1f
diff --git a/compiler/optimizing/code_generator_arm64.cc b/compiler/optimizing/code_generator_arm64.cc
index c00ab56..599185a 100644
--- a/compiler/optimizing/code_generator_arm64.cc
+++ b/compiler/optimizing/code_generator_arm64.cc
@@ -448,7 +448,7 @@
   }
 
   const char* GetDescription() const OVERRIDE { return "TypeCheckSlowPathARM64"; }
-  bool IsFatal() const { return is_fatal_; }
+  bool IsFatal() const OVERRIDE { return is_fatal_; }
 
  private:
   const bool is_fatal_;