Include PathV1.h only where it is used.

llvm-svn: 184090
diff --git a/clang/lib/Driver/WindowsToolChain.cpp b/clang/lib/Driver/WindowsToolChain.cpp
index 64625ed..da914be 100644
--- a/clang/lib/Driver/WindowsToolChain.cpp
+++ b/clang/lib/Driver/WindowsToolChain.cpp
@@ -18,6 +18,7 @@
 #include "llvm/Option/ArgList.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/PathV1.h"
 
 // Include the necessary headers to interface with the Windows registry and
 // environment.