s/ports/src/

Probably want to set DISTDIR=${DESTDIR}/usr/ports/distfiles here just in case there's environmental pollution which would send the distfiles into the wrong place.

Actually thinking about this a bit more -- the src.txz and ports.txz tarballs will go away at some point with pkgbase. Can we copy the trees directly rather than going through those? (Obviously we have a src tree at this point; I'm not immediately sure if we're guaranteed to have a ports tree mounted when this code runs but that's probably easily achievable.)

I think it's reasonable to do that, but separately from this change. But, is the change here just fxJ to -xfJ?

Yeah I have no problem with that change happening later. Just thought about it while looking at these bits.