flake.nix: Move vm out of nixosConfigurations so that checks work

flake.nix

@@ -77,15 +77,10 @@
       inherit (nixpkgs.legacyPackages.${system}) writeShellScript;
     in {
       default = let
-        vm =
-          (self.lib.makeNixosSystem {
-            inherit system;
-            extraModules = [(import ./configuration/hardware-specific/vm.nix)];
-          })
-          .config
-          .system
-          .build
-          .vm;
+        vm = self.lib.makeNixosSystem {
+          inherit system;
+          extraModules = [(import ./configuration/hardware-specific/vm.nix)];
+        };
 
         qemuNetOpts = self.lib.makeQemuNetOpts {
           "2222" = "2222";
@@ -98,7 +93,7 @@
         program = builtins.toString (writeShellScript "run-vm" ''
           export QEMU_OPTS="-m 3941 -smp 2 -display curses"
           export QEMU_NET_OPTS="${qemuNetOpts}"
-          "${vm}/bin/run-tlaternet-vm"
+          "${vm.config.system.build.vm}/bin/run-tlaternet-vm"
         '');
       };