Unstable builds on recent Nix

[Thesola10]

Currently testing on macOS Monterey with Nix 2.17, and I'm getting a few random filesystem errors, meaning somehow the exec* hooks aren't covering every process, or some system calls aren't hooked into. Building nixie from the fakedir environment always ends up failing with a random Is a directory or other derivation read error. This may indicate a race condition between threads of a single process.