If `UISTYLE` is not specified, Unison tries to auto-detect the UI style based on the available environment. On macOS this apparently means using `UISTYLE=mac`, it can't actually build this way in Nix.
If `UISTYLE` is not specified, Unison tries to auto-detect the UI style based on the available environment. On macOS this apparently means using `UISTYLE=mac`, it can't actually build this way in Nix.