"...PrivateStorageio.git" did not exist on "f62e0bead262cd71ad352e867c910229dd13db09"
Previously the Nix / Stack integration allowed for builds. However, this isn't how the real package for NixOS is actually built. Instead, that uses the Nix "haskell.nix" library and it was untested on CI and also broken.
This adds CI and fixes the failure.