patch by Yaron: Uses rand_s() from stdlib.h (when building for Windows)

llvm-svn: 192325
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 0354b92992a537330e67d280cf65a232a8ea1119
diff --git a/include/random b/include/random
index c5f7584..e5c08bc 100644
--- a/include/random
+++ b/include/random
@@ -3475,7 +3475,9 @@
 
 class _LIBCPP_TYPE_VIS random_device
 {
+#if !defined(_WIN32)
     int __f_;
+#endif // defined(_WIN32)
 public:
     // types
     typedef unsigned result_type;