Guard target dir check for non-Nones (#1593)
Summary:
Ensure the script still works locally when the target dir is not provided.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1593
Reviewed By: xuzhao9
Differential Revision: D45368425
Pulled By: janeyx99
fbshipit-source-id: fce06c1b45a67b6b2e5899ae11a02290cd30c8b6
