Wrong current path with custom build-type

My project has a custom build-type. After setup.hs is built, the resulting setup.exe is executed. In the past, it got executed in the project directory (the directory where the .cabal file resides). That is also the root directory of git.
One of the tasks of the custom setup is to fetch the commit id of git. However, this cannot be found now. Is this a bug, or is this a change on purpose? If the latter, is this documented somewhere?

* [Here is the build log at appveyor](https://ci.appveyor.com/project/Ampersand-Sentinel/ampersand/build/job/5f1fy95u4ofb2k8a)
* [Here are the sources at the point of this build](https://github.com/AmpersandTarski/Ampersand/tree/0117946195e56951367ed0d91eb40d0427ba003f)

NB: A [build of the same code with stack](https://travis-ci.org/AmpersandTarski/Ampersand/jobs/505190484) works fine