Test VM for the QuickPeep Nix Flake

To build and start a test VM, in this directory, with a copy of Nix that supports flakes, run:

nix build .#nixosConfigurations.testvm.config.system.build.vm -j8
./result/bin/run-nixos-vm

(An amd64 system is needed for now; otherwise you need to edit outputs.nix.)