Fix 32-bit builds, which otherwise fail with:

	python_function.cpp:798:15: error: format specifies type 'long' but the argument has type 'int' [-Werror,-Wformat]
  	796 |               "save_for_backward can only save variables, but argument %ld is of "

--- a/torch/csrc/autograd/python_function.cpp
+++ b/torch/csrc/autograd/python_function.cpp
@@ -798,7 +798,7 @@ static void _get_tensors_to_save(
               fmt::format(
                   "save_for_backward can only save variables, but argument {} is of "
                   "type {}",
-                  i,
+                  (long) i,
                   Py_TYPE(obj)->tp_name));
         }
       }