Make nix run .#vms.<system> work

flake.nix

@@ -39,7 +39,7 @@
       inherit (builtins) mapAttrs;
       inherit (lib) genAttrs mapAttrs';
       inherit (lib.flake) defaultSystems eachDefaultSystem;
-      inherit (lib.my) addPrefix;
+      inherit (lib.my) addPrefix mkApp;
 
       extendLib = lib: lib.extend (final: prev: {
         my = import ./util.nix { lib = final; };
@@ -77,12 +77,7 @@
 
       nixosConfigurations = import ./systems.nix { inherit lib pkgsFlakes inputs; modules = self.nixosModules; };
       systems = mapAttrs (_: system: system.config.system.build.toplevel) self.nixosConfigurations;
-      vms = mapAttrs (_: system: system.config.my.build.devVM) self.nixosConfigurations;
-
-      apps =
-        let apps' = { }
-          // addPrefix "vms/" (mapAttrs (name: vm: { type = "app"; program = "${vm}/bin/run-${name}-vm"; }) self.vms);
-        in { x86_64-linux = apps'; };
+      vms = mapAttrs (name: system: system.config.my.build.devVM) self.nixosConfigurations;
 
       devShell = genAttrs defaultSystems (system:
         let

modules/build.nix

@@ -1,6 +1,6 @@
 { lib, extendModules, modulesPath, baseModules, options, config, ... }:
 let
-  inherit (lib) mkOption;
+  inherit (lib) recursiveUpdate mkOption;
   inherit (lib.my) mkBoolOpt;
 
   cfg = config.my.build;
@@ -28,6 +28,7 @@ in
   };
 
   config.my.build = {
-    devVM = config.my.asDevVM.system.build.vm;
+    # The meta.mainProgram should probably be set upstream but oh well...
+    devVM = recursiveUpdate config.my.asDevVM.system.build.vm { meta.mainProgram = "run-${config.system.name}-vm"; };
   };
 }

util.nix

@@ -22,6 +22,7 @@ rec {
     };
 
   mkPkgs = path: args: genAttrs defaultSystems (system: import path (args // { inherit system; }));
+  mkApp = program: { type = "app"; inherit program; };
 
   mkOpt = type: default: mkOption { inherit type default; };
   mkBoolOpt = default: mkOption {