Windows support by Ruben Van Boxem.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@142235 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/locale b/include/locale
index aa99ff7..b2afbd4 100644
--- a/include/locale
+++ b/include/locale
@@ -192,7 +192,9 @@
 #include <nl_types.h>
 #endif  // !_WIN32
 
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
+#endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD