meson: Fix gst-launch build on UWP

The APIs we need from WinMM for higher timer resolution are only
available for non-UWP apps. The winmm library itself is still
available, so we need to disable the check.

Part-of: <gstreamer/gstreamer!890>
27 jobs for !890 with fix-uwp-winmm in 40 minutes and 33 seconds (queued for 7 seconds)
merge request