[Feature] option --ignore-chown

What do you think about adding a new option to bwrap which will ignore errors when programs attempt to run `chown`?

I think it's common in user namespaces to pretend to be root, so programs may expect the ability to `chown`. However if there UID 0 is just mapped to a regular user's UID this will fail. It would be convenient if I could ignore these calls.

This could be done fairly easily with libseccomp if bwrap would respond to seccomp notifications. See the python example: https://github.com/seccomp/libseccomp/blob/master/tests/58-live-tsync_notify.py

Related: https://github.com/containers/bubblewrap/issues/210