bug#62936: [core-updates] pre-inst-env no longer works

[Brian Cully via Bug reports for GNU Guix <bug-guix@gnu.org>]

I did a full rebuild before submitting this bug: bootstrap -> configure
-> make clean -> make.

FWIW, I still have the issue with ‘pre-inst-env’ when not run from
within ‘guix shell -D guix’, which is a step I have never previously
needed. As I just explained on IRC:

--8<---------------cut here---------------start------------->8---
<bjc> i'm confused why it's suddenly a problem, though. i've never needed to
      use ‘guix shell’ with pre-inst-env before  [15:41]
<bjc> ludo says it's libgit2 linking against an old libc, but i have no idea
      how that's even possible
<bjc> for one thing: my system has been reconfigured. all my packages are now
      running core-updates, and that includes libgit2. for another: doesn't
      libgit link with a specific path in /gnu/store, so it'll use whatever
      glibc it needs regardless of what's in my “system” configuration?
--8<---------------cut here---------------end--------------->8---

Even if this is some particular problem to my build environment somehow,
I'd love an explanation as to what's going on because I'm extremely
confused.

In case it matters, I've re-run ‘system reconfigure’ and ‘home
reconfigure’ since moving to core-updates, thinking maybe there's some
bootstrapping issue. I'm now 2 system and home generations into
core-updates, but I have the same problem.

Thanks,