Import prebuilt clang toolchain for linux.
diff --git a/linux-x64/clang/include/llvm/Linker/Linker.h b/linux-x64/clang/include/llvm/Linker/Linker.h
new file mode 100644
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+++ b/linux-x64/clang/include/llvm/Linker/Linker.h
@@ -0,0 +1,59 @@
+//===- Linker.h - Module Linker Interface -----------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LINKER_LINKER_H
+#define LLVM_LINKER_LINKER_H
+
+#include "llvm/ADT/StringSet.h"
+#include "llvm/Linker/IRMover.h"
+
+namespace llvm {
+class Module;
+class StructType;
+class Type;
+
+/// This class provides the core functionality of linking in LLVM. It keeps a
+/// pointer to the merged module so far. It doesn't take ownership of the
+/// module since it is assumed that the user of this class will want to do
+/// something with it after the linking.
+class Linker {
+  IRMover Mover;
+
+public:
+  enum Flags {
+    None = 0,
+    OverrideFromSrc = (1 << 0),
+    LinkOnlyNeeded = (1 << 1),
+  };
+
+  Linker(Module &M);
+
+  /// \brief Link \p Src into the composite.
+  ///
+  /// Passing OverrideSymbols as true will have symbols from Src
+  /// shadow those in the Dest.
+  ///
+  /// Passing InternalizeCallback will have the linker call the function with
+  /// the new module and a list of global value names to be internalized by the
+  /// callback.
+  ///
+  /// Returns true on error.
+  bool linkInModule(std::unique_ptr<Module> Src, unsigned Flags = Flags::None,
+                    std::function<void(Module &, const StringSet<> &)>
+                        InternalizeCallback = {});
+
+  static bool linkModules(Module &Dest, std::unique_ptr<Module> Src,
+                          unsigned Flags = Flags::None,
+                          std::function<void(Module &, const StringSet<> &)>
+                              InternalizeCallback = {});
+};
+
+} // End llvm namespace
+
+#endif