_CS_DARWIN_USER macros available on darwin>=9.  Thanks, Dave Odell!

llvm-svn: 201255
diff --git a/llvm/lib/Support/Path.cpp b/llvm/lib/Support/Path.cpp
index 1872af5..1e59c7a 100644
--- a/llvm/lib/Support/Path.cpp
+++ b/llvm/lib/Support/Path.cpp
@@ -508,8 +508,9 @@
 void system_temp_directory(bool erasedOnReboot, SmallVectorImpl<char> &result) {
   result.clear();
 
-#ifdef __APPLE__
+#if defined(_CS_DARWIN_USER_TEMP_DIR) && defined(_CS_DARWIN_USER_CACHE_DIR)
   // On Darwin, use DARWIN_USER_TEMP_DIR or DARWIN_USER_CACHE_DIR.
+  // macros defined in <unistd.h> on darwin >= 9
   int ConfName = erasedOnReboot? _CS_DARWIN_USER_TEMP_DIR
                                : _CS_DARWIN_USER_CACHE_DIR;
   size_t ConfLen = confstr(ConfName, 0, 0);