Windows support by Ruben Van Boxem.

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

include/stdexcept

diff --git a/include/stdexcept b/include/stdexcept
index d31dc8b..ef5de59 100644
--- a/include/stdexcept
+++ b/include/stdexcept
@@ -46,7 +46,9 @@
 #include <exception>
 #include <iosfwd>  // for string forward decl
 
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
+#endif
 
 namespace std  // purposefully not using versioning namespace
 {