pinwheel: Use pkgs.buildFHSUserEnv for pants

flake.nix

@@ -31,11 +31,6 @@
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
-    nix-alien = {
-      url = "github:thiagokokada/nix-alien";
-      inputs.nixpkgs.follows = "nixpkgs";
-    };
-
     pppdotpm-site = {
       url = "git+ssh://git@codeberg.org/ppp/ppp.pm-site.git?ref=main";
       inputs.nixpkgs.follows = "nixpkgs";