Replace string GNU Triples with llvm::Triple in MCSubtargetInfo and create*MCSubtargetInfo(). NFC.

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

Reviewers: rafael

Reviewed By: rafael

Subscribers: rafael, ted, jfb, llvm-commits, rengolin, jholewinski

Differential Revision: http://reviews.llvm.org/D10311

llvm-svn: 239467
diff --git a/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp b/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
index 50d4395..08499dc 100644
--- a/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
+++ b/llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
@@ -217,7 +217,7 @@
     // function that reside in TargetOptions.
     resetTargetOptions(F);
     I = llvm::make_unique<PPCSubtarget>(
-        TargetTriple, CPU,
+        Triple(TargetTriple), CPU,
         // FIXME: It would be good to have the subtarget additions here
         // not necessary. Anything that turns them on/off (overrides) ends
         // up being put at the end of the feature string, but the defaults