This should work around a current problems with AppVeyor.
The preview image might be unstable in the future. If that happens we can simply switch back.
However, the motivation is to avoid the current issues as cleanly as possible.
I believe msys still has no binary package for Unicorn. Therefore, a new issue will have to be created when #138 is closed.
For the record: we can return to the standard image since https://www.appveyor.com/updates/2018/05/16/
However, we can switch when it becomes necessary. There are no plans to switch back right now.
Closes #138 Closes #139
This should work around a current problems with AppVeyor. The preview image might be unstable in the future. If that happens we can simply switch back. However, the motivation is to avoid the current issues as cleanly as possible.
I believe msys still has no binary package for Unicorn. Therefore, a new issue will have to be created when #138 is closed.