clang: add support for asmjs arch and Emscripten OS

lib/Driver/ToolChains.h

 //===--- ToolChains.h - ToolChain Implementations ---------------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_H
@@ skipping 697 matching lines @@
   CXXStdlibType GetCXXStdlibType(const llvm::opt::ArgList &Args) const override;
 
   StringRef GetGCCLibAndIncVersion() const { return GCCLibAndIncVersion.Text; }
 
   static std::string GetGnuDir(const std::string &InstalledDir,
                                const llvm::opt::ArgList &Args);
 
   static StringRef GetTargetCPU(const llvm::opt::ArgList &Args);
 };
 
+// @LOCALMOD-START Emscripten
+/// EmscriptenToolChain - A toolchain for the Emscripten C/C++ to JS compiler.
+class LLVM_LIBRARY_VISIBILITY EmscriptenToolChain : public ToolChain {
+public:
+  EmscriptenToolChain(const Driver &D, const llvm::Triple &Triple,
+                      const llvm::opt::ArgList &Args)
+      : ToolChain(D, Triple, Args) {}
+  ~EmscriptenToolChain() override {}
+
+  bool IsMathErrnoDefault() const override { return false; }
+  bool IsObjCNonFragileABIDefault() const override { return true; }
+  bool isPICDefault() const override { return false; }
+  bool isPIEDefault() const override { return false; }
+  bool isPICDefaultForced() const override { return false; }
+};
+// @LOCALMOD-END Emscripten
+
 // @LOCALMOD-START
 class LLVM_LIBRARY_VISIBILITY NaCl_TC : public Generic_ELF {
 public:
   NaCl_TC(const Driver &D, const llvm::Triple &Triple,
           const llvm::opt::ArgList &Args);
 
   void
   AddClangSystemIncludeArgs(const llvm::opt::ArgList &DriverArgs,
                             llvm::opt::ArgStringList &CC1Args) const override;
   void
@@ skipping 127 matching lines @@
                        llvm::opt::ArgStringList &CC1Args) const override;
   void AddCXXStdlibLibArgs(const llvm::opt::ArgList &Args,
                            llvm::opt::ArgStringList &CmdArgs) const override;
 };
 
 } // end namespace toolchains
 } // end namespace driver
 } // end namespace clang
 
 #endif