flake.nix: add proper *-vm packages

flake.nix

@@ -216,21 +216,34 @@
         builtins.foldl' (result: host:
           let
             inherit (self.nixosConfigurations.${host}) config;
-            vmConfig = (nixpkgs.lib.nixosSystem {
-              modules = [ { inherit config; } ];
-            }).config;
           in
             result //
             nixpkgs.lib.optionalAttrs (config.system.build ? sdImage) {
               "${host}-sdImage" = config.system.build.sdImage;
             } //
-            # if you want to try your containers in a vm, turn off
-            # `boot.isContainer` just for testing.
-            nixpkgs.lib.optionalAttrs (config.system.build ? vm && !config.boot.isContainer) {
-              "${host}-vm" = vmConfig.system.build.vm
-                .overrideAttrs (oa: {
-                  meta.mainProgram = "run-${host}-vm";
-                });
+            nixpkgs.lib.optionalAttrs (config.system.build ? vm) {
+              # boot any machine in a microvm
+              "${host}-vm" = (self.nixosConfigurations.${host}
+                .extendModules {
+                  modules = [
+                    microvm.nixosModules.microvm
+                    {
+                      microvm = {
+                        mem = 2048;
+                        hypervisor = "qemu";
+                        socket = null;
+                        shares = [ {
+                          tag = "ro-store";
+                          source = "/nix/store";
+                          mountPoint = "/nix/.ro-store";
+                        } ];
+                      };
+                      boot.isContainer = lib.mkForce false;
+                      fileSystems."/".fsType = lib.mkForce "tmpfs";
+                    }
+                  ];
+                })
+                .config.microvm.declaredRunner;
             } //
             nixpkgs.lib.optionalAttrs (config.system.build ? tftproot) {
               "${host}-tftproot" = config.system.build.tftproot;