Apply the wrapper to the default vm

lib/config/custom-build-vm.nix

@@ -1,46 +1,66 @@
-{ config, lib, pkgs, ... }:
-let
-  createVmRunner =
-    vmVariant:
-      pkgs.writeShellApplication {
-        name = "run-${config.system.name}-vm";
-        text = ''
-          ${vmVariant.system.build.vm}/bin/run-${config.system.name}-vm
-        '';
+{ config, lib, options, pkgs, ... }: {
+  options = {};
+
+  config = {
+    # Replace native `qemu` with `remote-viewer`
+    system.build =
+      {
+        vm =
+          let
+            packageName = "custom-nixos-vm";
+
+            mergedSystem =
+              with options.system;
+              lib.mergeDefinitions
+                build.loc
+                build.type
+                (lib.lists.forEach
+                  (
+                    builtins.filter
+                      (item:
+                        !(lib.path.hasPrefix ./. (/. + item.file)))
+                      build.definitionsWithLocations)
+                  (item: { inherit (item) file value; }));
+          in
+            lib.mkForce (
+              if (mergedSystem.mergedValue.vm.name == packageName)
+              then
+                mergedSystem.mergedValue.vm
+              else
+                let
+                  wrapped = pkgs.writeShellApplication {
+                    name = "run-${config.system.name}-vm";
+                    text = ''
+                      ${mergedSystem.mergedValue.vm}/bin/run-${config.system.name}-vm
+                    '';
+                  };
+                in
+                  # Rename package to `nixos-vm`
+                  pkgs.symlinkJoin {
+                    name = packageName;
+                    paths = [ wrapped ];
+                  });
       };
-in
-  {
-    config = {
-      # Replace native `qemu` with `remote-viewer`
-      system.build =
-        with {
-          inherit (config.virtualisation)
-            vmVariantWithBootLoader
-          ;
-        };
-        {
-          vmWithBootLoader = createVmRunner vmVariantWithBootLoader;
-        };
 
-      virtualisation =
-        let vmConfig = {
-          boot.loader.efi.efiSysMountPoint = lib.mkForce "/boot";
+    virtualisation =
+      let vmConfig = {
+        boot.loader.efi.efiSysMountPoint = lib.mkForce "/boot";
 
-          virtualisation = {
-            qemu.options = [
-              "-display sdl"
-            ];
+        virtualisation = {
+          qemu.options = [
+            "-display sdl"
+          ];
 
-            sharedDirectories = {
-              hostKeys = {
-                source = "/etc/ssh";
-                target = "/etc/ssh";
-              };
+          sharedDirectories = {
+            hostKeys = {
+              source = "/etc/ssh";
+              target = "/etc/ssh";
             };
           };
         };
-        in {
-          vmVariantWithBootLoader = vmConfig;
-        };
-    };
-  }
+      };
+      in {
+        vmVariantWithBootLoader = vmConfig;
+      };
+  };
+}