clang: add support for asmjs arch and Emscripten OS

lib/Driver/Driver.cpp

 //===--- Driver.cpp - Clang GCC Compatible Driver -------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "clang/Driver/Driver.h"
@@ skipping 1996 matching lines @@
       break;
     case llvm::Triple::Minix:
       TC = new toolchains::Minix(*this, Target, Args);
       break;
     case llvm::Triple::Linux:
       if (Target.getArch() == llvm::Triple::hexagon)
         TC = new toolchains::Hexagon_TC(*this, Target, Args);
       else
         TC = new toolchains::Linux(*this, Target, Args);
       break;
+    // @LOCALMOD-START Emscripten
+    case llvm::Triple::Emscripten:
+      TC = new toolchains::EmscriptenToolChain(*this, Target, Args);
+      break;
+    // @LOCALMOD-END Emscripten
     // @LOCALMOD-START
     case llvm::Triple::NaCl:
       TC = new toolchains::NaCl_TC(*this, Target, Args);
       break;
     // @LOCALMOD-END
     case llvm::Triple::Solaris:
       TC = new toolchains::Solaris(*this, Target, Args);
       break;
     case llvm::Triple::Win32:
       switch (Target.getEnvironment()) {
@@ skipping 116 matching lines @@
   } else {
     ExcludedFlagsBitmask |= options::CLOption;
   }
 
   return std::make_pair(IncludedFlagsBitmask, ExcludedFlagsBitmask);
 }
 
 bool clang::driver::isOptimizationLevelFast(const llvm::opt::ArgList &Args) {
   return Args.hasFlag(options::OPT_Ofast, options::OPT_O_Group, false);
 }