Pull Request: Detect the right com.apple.boot file on custom macs

[michael...@gmail.com]

Hi,

I've recently opened a pull request [1] and it would
be nice, if it could be merged into the master branch.

Please let me know if there are any questions or
improvements to my change!

Thanks, Michael

[1] https://github.com/apenwarr/sshuttle/pull/15