replicate a terrible hack to fix a build error on VC++

llvm-svn: 120039
diff --git a/clang/lib/Basic/FileSystemStatCache.cpp b/clang/lib/Basic/FileSystemStatCache.cpp
index 26e9d2f..6457414 100644
--- a/clang/lib/Basic/FileSystemStatCache.cpp
+++ b/clang/lib/Basic/FileSystemStatCache.cpp
@@ -15,6 +15,10 @@
 #include "llvm/System/Path.h"
 using namespace clang;
 
+#if defined(_MSC_VER)
+#define S_ISDIR(s) (_S_IFDIR & s)
+#endif
+
 MemorizeStatCalls::LookupResult
 MemorizeStatCalls::getStat(const char *Path, struct stat &StatBuf) {
   LookupResult Result = statChained(Path, StatBuf);