Use the new Windows environment for target detection

This follows the LLVM change to canonicalise the Windows target triple
spellings.  Rather than treating each Windows environment as a single entity,
the environments are now modelled properly as an environment.  This is a
mechanical change to convert the triple use to reflect that change.

llvm-svn: 204978
diff --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
index e661c66..01eced2 100644
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/clang/lib/Basic/TargetInfo.cpp
@@ -83,7 +83,7 @@
   ComplexLongDoubleUsesFP2Ret = false;
 
   // Set the C++ ABI based on the triple.
-  TheCXXABI.set(Triple.getOS() == llvm::Triple::Win32
+  TheCXXABI.set(Triple.isKnownWindowsMSVCEnvironment()
                     ? TargetCXXABI::Microsoft
                     : TargetCXXABI::GenericItanium);