Driver: Fix thinko in Darwin host identification.

llvm-svn: 66889
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 4efd460..fdc60da 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -583,7 +583,7 @@
   } else
     Arch = Triple;
 
-  if (memcmp(&Platform[0], "darwin", 6) == 0)
+  if (memcmp(&OS[0], "darwin", 6) == 0)
     return new DarwinHostInfo(Arch.c_str(), Platform.c_str(), OS.c_str());
     
   return new UnknownHostInfo(Arch.c_str(), Platform.c_str(), OS.c_str());