Allow option for using system tar

[SlexAxton]

Some of our machines barf all over modes when the node implementation is used.

We've successfully used https://github.com/jbalogh/freight/tree/tar for a bit. Probably safe as an option --with-system-tar or whatever.

[darcyclarke]

@SlexAxton do you know what's happened to @jbalogh's fork? Did this get merged in or did the project move?

[vladikoff]

^ https://github.com/jbalogh/freight-server/tree/tar

[SlexAxton]

Ah. We moved to npm enterprise, so he probably deleted it. I'll see if I can't trace something back, it's not a huge change.