Add a build for a qemu virtual machine.

nix/configuration/flake.nix

@@ -63,5 +63,46 @@
           })
         ];
       };
+      nixosConfigurations.odoqemu = nixpkgs.lib.nixosSystem rec {
+        system = "x86_64-linux";
+        specialArgs = {
+          pkgs-b93b4e9b5 = import nixpkgs-b93b4e9b5 {
+            inherit system;
+            # config.allowUnfree = true;
+          };
+          pkgs-unstable = import nixpkgs-unstable {
+            inherit system;
+            # config.allowUnfree = true;
+          };
+        };
+        modules = [
+          impermanence.nixosModules.impermanence
+          home-manager.nixosModules.home-manager
+          {
+            home-manager.useGlobalPkgs = true;
+            home-manager.useUserPackages = true;
+          }
+          ./configuration.nix
+          ({lib, ...}: {
+            imports = [ <nixpkgs/nixos/modules/virtualisation/qemu-vm.nix> ];
+            virtualisation.qemu.options = [
+              "-device virtio-vga"
+            ];
+            virtualisation.vmVariant = {
+              # following configuration is added only when building VM with build-vm
+              virtualisation = {
+                memorySize = 2048; # Use 2048MiB memory.
+                cores = 3;
+                graphics = false;
+              };
+            };
+            networking.dhcpcd.enable = lib.mkForce true;
+            networking.useDHCP = lib.mkForce true;
+            boot.loader.efi.canTouchEfiVariables = lib.mkForce true;
+            # doas nixos-rebuild build-vm --flake .#odoqemu
+            #./result/bin/run-nixos-vm
+          })
+        ];
+      };
     };
 }