[Support] Add missing files from e823068306.

llvm/lib/Support/CMakeLists.txt

@@ -91,6 +91,7 @@ add_llvm_component_library(LLVMSupport
   ELFAttributes.cpp
   Error.cpp
   ErrorHandling.cpp
+  ExtensibleRTTI.cpp
   FileCheck.cpp
   FileCollector.cpp
   FileUtilities.cpp

llvm/lib/Support/ExtensibleRTTI.cpp

@@ -0,0 +1,13 @@
+//===----- lib/Support/ExtensibleRTTI.cpp - ExtensibleRTTI utilities ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/ExtensibleRTTI.h"
+
+void llvm::RTTIRoot::anchor() {}
+char llvm::RTTIRoot::ID = 0;