Make zsh install conditional.

nix/configuration/hosts/neelix/default.nix

@@ -31,4 +31,5 @@
   me.lvfs.enable = true;
   me.sound.enable = true;
   me.zrepl.enable = true;
+  me.zsh.enable = true;
 }

nix/configuration/hosts/odo/default.nix

@@ -58,4 +58,5 @@
   me.wasm.enable = true;
   me.waybar.enable = true;
   me.zrepl.enable = true;
+  me.zsh.enable = true;
 }

nix/configuration/roles/zsh/default.nix

@@ -55,6 +55,18 @@ in
 {
   imports = [ ];
 
+  options.me = {
+    zsh.enable = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      example = true;
+      description = "Whether we want to install zsh.";
+    };
+  };
+
+  config = lib.mkIf config.me.zsh.enable (
+    lib.mkMerge [
+      {
         environment.systemPackages = with pkgs; [
           zsh
         ];
@@ -88,3 +100,6 @@ in
           };
         };
       }
+    ]
+  );
+}