extract uimage output module into own file

modules/outputs.nix

@@ -14,6 +14,7 @@ in
     ./outputs/squashfs.nix
     ./outputs/vmroot.nix
     ./outputs/extlinux.nix
+    ./outputs/uimage.nix
     ./outputs/updater
   ];
   options = {
@@ -41,16 +42,6 @@ in
           Compiled device tree (FDT) for the target device
         '';
       };
-      uimage = mkOption {
-        type = types.package;
-        internal = true;
-        description = ''
-          uimage
-          ******
-
-          Combined kernel and FDT in uImage (U-Boot compatible) format
-        '';
-      };
       tplink-safeloader = mkOption {
         type = types.package;
       };
@@ -100,13 +91,6 @@ in
           "${o.kernel.headers}/include"
         ];
       };
-      uimage = liminix.builders.uimage {
-        commandLine = concatStringsSep " " config.boot.commandLine;
-        inherit (config.boot) commandLineDtbNode;
-        inherit (config.hardware) loadAddress entryPoint alignment;
-        inherit (config.boot) imageFormat;
-        inherit (o) kernel dtb;
-      };
       rootdir =
         let
           inherit (pkgs.pkgsBuildBuild) runCommand;

modules/outputs/uimage.nix

@@ -0,0 +1,30 @@
+{
+  config,
+  pkgs,
+  lib,
+  ...
+}:
+let
+  inherit (lib) mkOption types concatStringsSep;
+  inherit (pkgs) liminix writeText;
+  o = config.system.outputs;
+in
+{
+  options.system.outputs.uimage = mkOption {
+    type = types.package;
+    internal = true;
+    description = ''
+      uimage
+      ******
+
+      Combined kernel and FDT in uImage (U-Boot compatible) format
+    '';
+  };
+  config.system.outputs.uimage = liminix.builders.uimage {
+    commandLine = concatStringsSep " " config.boot.commandLine;
+    inherit (config.boot) commandLineDtbNode;
+    inherit (config.hardware) loadAddress entryPoint alignment;
+    inherit (config.boot) imageFormat;
+    inherit (o) kernel dtb;
+  };
+}