clang: add support for asmjs arch and Emscripten OS

lib/Driver/ToolChains.h

Index: lib/Driver/ToolChains.h
diff --git a/lib/Driver/ToolChains.h b/lib/Driver/ToolChains.h
index 467072edbc3413ac9dd856d5f877c89f6768e914..c6f6bd4dcf65780c86c576796cf9e0924476c292 100644
--- a/lib/Driver/ToolChains.h
+++ b/lib/Driver/ToolChains.h
@@ -715,6 +715,22 @@ public:
   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);
+  ~EmscriptenToolChain();
+
+  bool IsMathErrnoDefault() const;

[jvoung (off chromium), 2015/03/20 17:07:07]

Indicate these methods are "override" ?

Why not just inline the bodies? Most of them do that except for TCEToolChain.

[JF, 2015/03/20 18:49:38]

Done.

+  bool IsObjCNonFragileABIDefault() const;
+  bool isPICDefault() const;
+  bool isPIEDefault() const;
+  bool isPICDefaultForced() const;
+};
+// @LOCALMOD-END Emscripten
+
 // @LOCALMOD-START
 class LLVM_LIBRARY_VISIBILITY NaCl_TC : public Generic_ELF {
 public: