G M:  Restore the ability for libcxx to compile again on mingw 64.

llvm-svn: 190837
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 5f878d4bd2730576533183b62910c8a1c3d94119
diff --git a/include/algorithm b/include/algorithm
index e3b0882..367489f 100644
--- a/include/algorithm
+++ b/include/algorithm
@@ -631,6 +631,9 @@
 #if defined(__IBMCPP__)
 #include "support/ibm/support.h"
 #endif
+#if defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
+#include "support/win32/support.h"
+#endif
 
 #include <__undef_min_max>