Work around missing wait_for declaration

Certain older SDKs don't declare the specific wait_for overload but
still uses it. So, we declare it.

Also add the factorycacheregistration include to wipe out any factory
that may be created and cached in the TU.

Change-Id: I778ab1b8724306b17bb6a2daa0b7364f268ded83
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

src/plugins/platforms/windows/qwindowsintegration.cpp

@@ -62,6 +62,16 @@
 #include "qwindowsopengltester.h"
 
 #if QT_CONFIG(cpp_winrt)
+#include <winrt/base.h>
+#include <QtCore/private/qfactorycacheregistration_p.h>
+// Workaround for Windows SDK bug.
+// See https://github.com/microsoft/Windows.UI.Composition-Win32-Samples/issues/47
+namespace winrt::impl
+{
+    template <typename Async>
+    auto wait_for(Async const& async, Windows::Foundation::TimeSpan const& timeout);
+}
+
 #  include <winrt/Windows.UI.Notifications.h>
 #  include <winrt/Windows.Data.Xml.Dom.h>
 #  include <winrt/Windows.Foundation.h>