systemconfig: chown files if uid/gid > 0

tests/jffs2/configuration.nix

@@ -1,8 +1,19 @@
 { config, pkgs, lib, ... } :
-{
+let
+  inherit (pkgs.pseudofile) dir symlink;
+in {
   imports = [
     ../../vanilla-configuration.nix
+    ../../modules/squashfs.nix
     ../../modules/jffs2.nix
   ];
   config.rootfsType = "jffs2";
+  config.filesystem = dir {
+    hello = {
+      type = "f";
+      uid = 7;
+      gid = 24;
+      file = "hello world";
+    };
+  };
 }