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/bitset b/include/bitset
index 4d9efd9..c970f32 100644
--- a/include/bitset
+++ b/include/bitset
@@ -113,7 +113,9 @@
 
 */
 
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
+#endif
 
 #include <__config>
 #include <__bit_reference>