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/cassert b/include/cassert
index 7337b16..3775990 100644
--- a/include/cassert
+++ b/include/cassert
@@ -20,4 +20,6 @@
 #include <__config>
 #include <assert.h>
 
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
+#endif