buildPython*: simplify updateScript

updateScript accepts a list, in which case, it will execute the head with the
tail as arguments. Switching to this style will allow us to get rid of the need
to create extra script doing just that.

pkgs/development/interpreters/python/mk-python-derivation.nix

@@ -113,9 +113,6 @@ let self = toPythonModule (python.stdenv.mkDerivation (builtins.removeAttrs attr
 passthru = {
   updateScript = let
     filename = builtins.head (lib.splitString ":" self.meta.position);
-  in writeScript "update-python" ''
-    #!${python.stdenv.shell}
-    ${update-python-libraries} ${filename}
-  '';
+  in [ update-python-libraries filename ];
 };
 in lib.extendDerivation true passthru self