Fix the Appveyor build

[ndmitchell]

https://ci.appveyor.com/project/ndmitchell/filepath is failing. The problem is that it doesn't find time on the plan. Trying the same project but renaming filepath to anything else fixes the issue, so it seems to be that by putting filepath in the plan it invalidates time somehow. A Stack bug, but I'm not convinced one they'll necessarily want to fix, as overwriting filepath is an odd thing to do.

[ndmitchell]

No progress on this from the Stack side, and it's a bit of an odd case, so I remove the Appveyor script in 2b7adb0.

[Rufflewind]

FWIW, directory was able to migrate from AppVeyor + Travis CI to a hand-crafted GitHub Actions config: https://github.com/haskell/directory/blob/master/.github/workflows/build.yml

The initial setup took some time to figure out -- the lack of standardization didn't help -- but past the learning curve it's actually pretty convenient and low-maintenance. Not having to deal with two CI services (AppVeyor + Travis CI) was a nice perk.

[ndmitchell]

I've moved all my other projects to GitHub actions and agree it's clearly the best way to go. However, I'm in the process of transferring maintainership, so think the new maintainer should have choice of which CI to use, and how to configure it etc: #79

[hasufell]

#89