pkg-stage: Improve symlink creation

[emaste]

Summary

In normal use it doesn't matter, but during development this might be run in a partially populated leftover tree.

[emaste]

ping

[jrtc27]

These probably want -h too? pkg.pkg less interesting, but PKG_ALTABI surely that can go quite wrong if not?

[ivy]

i think ${PKG_ALTABI} definitely needs -h here. that will break Linux, but i'm fairly sure the pkgbase release stuff doesn't work on Linux anyway.

[emaste]

I found this again in my WIP tree after looking at D56656. (The comment I left there is presumably prompted by a vague memory of this.)

I'll update this to -hfs for now

[jrtc27]

Oh, I always forget which way round -h and -n are. -n is the one you want, as we accept both as meaning the same thing, but coreutils only accepts -n.