python3: fix wrong platform libs when cross-compiling

see https://github.com/NixOS/nixpkgs/pull/169475#issuecomment-1129517328

patch by adisbladis

Co-authored-by: adisbladis <adisbladis@gmail.com>

pkgs/development/interpreters/python/cpython/default.nix

@@ -82,7 +82,7 @@ let
 
   passthru = let
     # When we override the interpreter we also need to override the spliced versions of the interpreter
-    inputs' = lib.filterAttrs (_: v: ! lib.isDerivation v) inputs;
+    inputs' = lib.filterAttrs (n: v: ! lib.isDerivation v && n != "passthruFun") inputs;
     override = attr: let python = attr.override (inputs' // { self = python; }); in python;
   in passthruFun rec {
     inherit self sourceVersion packageOverrides;