treewide: remove bash snippets in flags

Co-Authored-By: Jan Tojnar <jtojnar@gmail.com>

pkgs/games/mnemosyne/default.nix

@@ -33,17 +33,18 @@ python.pkgs.buildPythonApplication rec {
   # No tests/ directrory in tarball
   doCheck = false;
 
-  dontWrapQtApps = true;
-  makeWrapperArgs = [
-    "\${qtWrapperArgs[@]}"
-  ];
-
   postInstall = ''
     mkdir -p $out/share
     mv $out/${python.sitePackages}/$out/share/locale $out/share
     rm -r $out/${python.sitePackages}/nix
   '';
 
+  dontWrapQtApps = true;
+
+  preFixup = ''
+    makeWrapperArgs+=("''${qtWrapperArgs[@]}")
+  '';
+
   meta = {
     homepage = https://mnemosyne-proj.org/;
     description = "Spaced-repetition software";