Replace string GNU Triples with llvm::Triple in TargetMachine. NFC.

Summary:
For the moment, TargetMachine::getTargetTriple() still returns a StringRef.

This continues the patch series to eliminate StringRef forms of GNU triples
from the internals of LLVM that began in r239036.

Reviewers: rengolin

Reviewed By: rengolin

Subscribers: ted, llvm-commits, rengolin, jholewinski

Differential Revision: http://reviews.llvm.org/D10362

llvm-svn: 239554
diff --git a/llvm/lib/Target/TargetMachine.cpp b/llvm/lib/Target/TargetMachine.cpp
index 0488126..0b05303 100644
--- a/llvm/lib/Target/TargetMachine.cpp
+++ b/llvm/lib/Target/TargetMachine.cpp
@@ -38,7 +38,7 @@
 //
 
 TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
-                             StringRef TT, StringRef CPU, StringRef FS,
+                             const Triple &TT, StringRef CPU, StringRef FS,
                              const TargetOptions &Options)
     : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),
       TargetFS(FS), CodeGenInfo(nullptr), AsmInfo(nullptr), MRI(nullptr),