xbps-src: drop fakeroot; xbps-create(8) is our friend.

- This should work for almost 90% current packages, as reported by OpenBSD/ports.
- Packages that use install -o <user> -g <group>  will get fixed progressively.
- xbps-create(8) by default sets pkg files as 0:0, if any pkg needs special
  permissions those can be set via INSTALL scripts (for now).
base-chroot: chroot-fakeroot is gone; thanks for your service.
xbps-src: cleanup signal handler catching SIGINT and SIGTERM.

- catching SIGHUP is meaningless.
- there's no point in clearning wkrsrc or removing autodeps, this is left
  intact right now; this could be useful to have.
base-chroot-musl: catch up with base-chroot.