Build windows job flaking

The "build windows" job is flaking and causing merge queue failures.

https://github.com/matrix-org/matrix-js-sdk/actions/runs/26808211350/job/79031707633 apparently failed in the post-run step of setup-node when making the new cache (so could be disk space related although I would expect a sensible error from tar).

Under zero flake tolerance policy, we need to find some way to make this not flake, however right now I'm at a bit of a loss for what that would be other than moving the job off GHA (buildjet maybe?)

If you see this, please add more instances here so we can at least try to establish a pattern of failure.