Use GetLinkerPath utility function to find linker for NaCl toolchain

[dschuff]

Summary

This is more consistent with other targets and also makes the -fuse-ld
flag work.

[jvoung]

Worth adding a test case to test/Driver/fuse-ld.c ?

Otherwise LGTM

[dschuff]

• broken test. uses system ld.gold

[dschuff]

argh, I keep forgetting that 'git svn dcommit' commits all of your local git commits individually. Sorry about the noise.

cfe/trunk/lib/Driver/ToolChains.cpp

case llvm::Triple::mipsel: {
     file_paths.push_back(ToolPath + "mipsel-nacl");
     break;
   }
   default:
     break;
   }
 
   // Use provided linker, not system linker
-  Linker = GetProgramPath("ld");
+  Linker = GetLinkerPath();
   NaClArmMacrosPath = GetFilePath("nacl-arm-macros.s");
 }
 
 void NaClToolChain::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
                                               ArgStringList &CC1Args) const {
   const Driver &D = getDriver();
   if (DriverArgs.hasArg(options::OPT_nostdinc))
     return;