Previously `cpu-flush` option existed as a boolean or integer argument, which is a bit counter-intuitive because for argparse, any non-empty string such as `False` will be parsed to `True` when using as a boolean and integer a little bit vague here IMHO. This PR used a function from `distutils` to directly parse input string to boolean, which makes the usage more stragiht-forward like `--cpu-flush True` or `--cpu-flush False`. Meanwhile it still supports usage of `0/1` and made sure the argument is always required.
Xiyou Zhou
25db38105d