The Wine tests are annoying, because they frequently fail (for more than a decade now), with no fix in sight.

Also, they are less useful than running on a real Windows.

My suggestion would be to replace the win64-cross CI task with one on GitHub Actions, using a real Windows. The cross compilation would still be done normally (to mimic guix), inside WSL. However, the unit tests would be run on the real Windows.

I won't be working on this myself, but I am happy to answer any questions on how to implement this, if they arise.