nix: reworked nixosModules system

nix/nixosModules/default.nix

@@ -1,11 +1,26 @@
-{
-  flake.nixosModules = {
-    # Shared between darwin and nix
-    _.imports = [
-      ./sudo-conf.nix
-      ./system-nixconf.nix
-    ];
+{ lib, ... }:
 
-    layouts = ./layouts;
+let
+  toModule = name: ./${name};
+
+  sharedModuleNames = [
+    "sudo-conf"
+    "system-nixconf"
+  ];
+  moduleNames = [ "layouts" ];
+
+  sharedModules = lib.attrsets.genAttrs sharedModuleNames toModule;
+
+  eachModule = lib.attrsets.genAttrs (sharedModuleNames ++ moduleNames) toModule;
+
+  allModules.imports = map toModule (sharedModuleNames ++ moduleNames);
+in
+
+{
+  flake.nixosModules = eachModule // {
+    # Shared between darwin and nix
+    shared = sharedModules;
+
+    _ = allModules;
   };
 }