Uninstall nixpkgs only after install

scripts/lib/action.fish

@@ -20,9 +20,8 @@ function runActionSetup -V dir
 end
 
 function disposeAction
-    runHook actionPostRun || true
-    and uninstallNixPkgs
     and sudo git config remove-section --system safe || true
+    runHook actionPostRun || true
 end
 
 function runAction -V dir
@@ -62,6 +61,7 @@ function runSetupUserAction -V dir
 
             and sudo --preserve-env --set-home --user "$name" $cmdline
             disposeAction
+            uninstallNixPkgs
             rm "$sudoConfig"
             userdel -rf "$name"
         end