Windows support by Ruben Van Boxem.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@142235 91177308-0d34-0410-b5e6-96231b3b80d8

include/stack

diff --git a/include/stack b/include/stack
index 3d72f96..59906bd 100644
--- a/include/stack
+++ b/include/stack
@@ -85,7 +85,9 @@
 #include <__config>
 #include <deque>
 
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
+#endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD