Investigate moving windows builds from AppVeyor to GitLab Windows
This was announced recently:
AppVeyor is pretty slow, limiting free plans to one parallel job running at once - in practice this means it can take over half an hour for builds and tests to run on Windows.
But GitLab CI is free for Open Source projects like Graphviz, so we could run the jobs in parallel.
Today, the windows jobs don't run at pull-request time, only after merging (probably because they're so slow). It would be good to make them fast so they can run at pull-request time.
It's a pity that we currently don't run the Windows builds in the test stage before deploy because then it doesn't get run for merge requests. @ellson Can we can change this? Or don't you want to delay the deploy with the long Windows builds?