NixOSConfig/lib/config/custom-build-vm.nix

{ config, lib, pkgs, ... }: {
  config = {
    # Replace native `qemu` with `remote-viewer`
    system.build = {
      vmWithBootLoader = pkgs.writeShellApplication {
        name = "run-${config.system.name}-vm";
        text = ''
          ${config.virtualisation.vmVariant.system.build.vm}/bin/run-${config.system.name}-vm
        '';
      };
    };

    virtualisation =
      let vmConfig = {
        boot.loader.efi.efiSysMountPoint = lib.mkForce "/boot";

        virtualisation = {
          qemu.options = [
            "-display sdl"
          ];

          sharedDirectories = {
            hostKeys = {
              source = "/etc/ssh";
              target = "/etc/ssh";
            };
          };
        };
      };
      in {
        vmVariant = vmConfig;
        vmVariantWithBootLoader = vmConfig;
      };
  };
}