nixos: use pkgsi686Linux for pkgs_i686 (#24772)

nixos/modules/misc/extra-arguments.nix

@@ -2,16 +2,6 @@
 
 {
   _module.args = {
-    pkgs_i686 = import ../../.. {
-      system = "i686-linux";
-      # FIXME: we enable config.allowUnfree to make packages like
-      # nvidia-x11 available. This isn't a problem because if the user has
-      # ‘nixpkgs.config.allowUnfree = false’, then evaluation will fail on
-      # the 64-bit package anyway. However, it would be cleaner to respect
-      # nixpkgs.config here.
-      config.allowUnfree = true;
-    };
-
     utils = import ../../lib/utils.nix pkgs;
   };
 }

nixos/modules/misc/nixpkgs.nix

@@ -42,6 +42,8 @@ let
     merge = lib.mergeOneOption;
   };
 
+  _pkgs = import ../../.. config.nixpkgs;
+
 in
 
 {
@@ -97,6 +99,9 @@ in
   };
 
   config = {
-    _module.args.pkgs = import ../../.. config.nixpkgs;
+    _module.args = {
+      pkgs = _pkgs;
+      pkgs_i686 = _pkgs.pkgsi686Linux;
+    };
   };
 }