Attempt to fix unit tests

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@140748 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/unittests/AST/APValueTest.cpp b/unittests/AST/APValueTest.cpp
index 98cb086..5ac454d 100644
--- a/unittests/AST/APValueTest.cpp
+++ b/unittests/AST/APValueTest.cpp
@@ -31,6 +31,10 @@
     }
 
     StringRef get() const { return LastDiagnostic; }
+
+    virtual DiagnosticConsumer *clone(DiagnosticsEngine &Diags) const {
+      return new LastDiagnosticString();
+    }
   };
 
   const IntrusiveRefCntPtr<DiagnosticIDs> DiagIDs;