python3Packages.cupy: pass custom stdenv to buildPythonApplication with an override

Passing `stdenv` directly to `buildPythonPackage` or `buildPythonApplication`
is deprecated with `oldestSupportedRelease = 2511`.

pkgs/development/python-modules/cupy/default.nix

@@ -49,13 +49,11 @@ let
       outpaths ++ lib.concatMap (outpath: lib.map (output: outpath.${output}) outpath.outputs) outpaths;
   };
 in
-buildPythonPackage rec {
+buildPythonPackage.override { stdenv = cudaPackages.backendStdenv; } rec {
   pname = "cupy";
   version = "13.6.0";
   pyproject = true;
 
-  stdenv = cudaPackages.backendStdenv;
-
   src = fetchFromGitHub {
     owner = "cupy";
     repo = "cupy";