scons: Add passthru.py2 for backward compatibility

Not all packages build with Python 3, see #75877. The goal is to get rid
of Python 2 but this approach ensures a smoother transition.

pkgs/games/vdrift/default.nix

@@ -20,8 +20,8 @@ let
       sha256 = "001wq3c4n9wzxqfpq40b1jcl16sxbqv2zbkpy9rq2wf9h417q6hg";
     };
 
-    nativeBuildInputs = [ pkgconfig ];
-    buildInputs = [ scons libGLU libGL SDL2 SDL2_image libvorbis bullet curl gettext ];
+    nativeBuildInputs = [ pkgconfig scons.py2 ];
+    buildInputs = [ libGLU libGL SDL2 SDL2_image libvorbis bullet curl gettext ];
 
     patches = [ ./0001-Ignore-missing-data-for-installation.patch ];