Nix and BSD: NetBSD
As announced on the Nix discourse:
We can also cross compile OpenBSD binaries now!
Nixpkgs branch: https://github.com/obsidiansystems/nixpkgs/tree/openbsd-rollup (will be making PRs from here and force pushing it, be warned)
Command:
nix-build --arg crossSystem '{ system = "x86_64-openbsd"; isStatic = true;