New comment by xelxebar on void-packages repository

https://github.com/void-linux/void-packages/pull/14758#issuecomment-537281499

Comment:
> I rather do not want same files to be managed by both xbps and jpkg. 

Yeah, ideally we could create a clean separation, but I'm not sure we have a whole lot of room to wiggle. J needs some of these files (*e.g.* `system/util/boot.ijs`) in order to bootstrap. I think the best we can do is find a minimal set with which to mark in `mutable_files`.