Bug fix for cpu userbenchmark (#1948)
Summary:
[commit 2d05303](https://github.com/pytorch/benchmark/commit/2d05303a5432c9b5b63558f22bfd43a51b029876) introduced a bug where `int`s get passed into `subprocess.run()` inside the `cmd` argument, causing a TypeError `expected str, bytes or os.PathLike object, not int` for every cpu benchmark. As a fix, convert `cmd` into a list of strings before using it.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1948
Reviewed By: davidberard98
Differential Revision: D49833578
Pulled By: xuzhao9
fbshipit-source-id: 8e45c462d8154c5d70176d4efb904ff54040126d
