StringRef-ize the TargetInfo::ConstraintInfo constructor.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@94916 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Basic/Targets.cpp b/lib/Basic/Targets.cpp
index 926d78b..5db6aed 100644
--- a/lib/Basic/Targets.cpp
+++ b/lib/Basic/Targets.cpp
@@ -157,7 +157,7 @@
     return "__TEXT,__ustring";
   }
 
-  virtual std::string isValidSectionSpecifier(const llvm::StringRef &SR) const {
+  virtual std::string isValidSectionSpecifier(llvm::StringRef SR) const {
     // Let MCSectionMachO validate this.
     llvm::StringRef Segment, Section;
     unsigned TAA, StubSize;