PNaClTargetInfo: add __ELF__, _REENTRANT and _GNU_SOURCE defines and update the test.

lib/Basic/Targets.cpp

 //===--- Targets.cpp - Implement -arch option and targets -----------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements construction of a TargetInfo object from a
@@ skipping 2852 matching lines @@
   void getDefaultFeatures(const std::string &CPU,
                           llvm::StringMap<bool> &Features) const {
   }
   virtual void getArchDefines(const LangOptions &Opts,
                               MacroBuilder &Builder) const {
     Builder.defineMacro("__le32__");
     Builder.defineMacro("__pnacl__");
   }
   virtual void getTargetDefines(const LangOptions &Opts,
                                 MacroBuilder &Builder) const {
+    DefineStd(Builder, "unix", Opts);
+    Builder.defineMacro("__ELF__");
+    if (Opts.POSIXThreads)
+      Builder.defineMacro("_REENTRANT");
+    if (Opts.CPlusPlus)
+      Builder.defineMacro("_GNU_SOURCE");
+
     Builder.defineMacro("__native_client__");
     getArchDefines(Opts, Builder);
   }
   virtual void getTargetBuiltins(const Builtin::Info *&Records,
                                  unsigned &NumRecords) const {
   }
   virtual const char *getVAListDeclaration() const {
     return "typedef struct __va_list_tag {"
            "  void* ptr;"
            "  void* padding1;"
@@ skipping 286 matching lines @@
   // need to pass the minuses.
   Opts.Features.clear();
   for (llvm::StringMap<bool>::const_iterator it = Features.begin(),
          ie = Features.end(); it != ie; ++it)
     Opts.Features.push_back(std::string(it->second ? "+" : "-") +
                             it->first().str());
   Target->HandleTargetFeatures(Opts.Features);
 
   return Target.take();
 }