[regression] error: chmod operation not permitted

[piegamesde]

Describe the bug

I just upgraded my Nix from 2.3 to 2.8, and now collecting garbage fails:

finding garbage collector roots...
removing stale temporary roots file '/nix/var/nix/temproots/16098'
deleting garbage...
deleting '/nix/store/2h7xciwzgqc3rlssfm6njyz97699n4k5-root-path-files'
1 store paths deleted, 0.00 MiB freed
error: chmod '/nix/store/2h7xciwzgqc3rlssfm6njyz97699n4k5-root-path-files': Operation not permitted

Steps To Reproduce

1. nix-store --gc

Expected behavior

It doesn't fail. In case this is a one-off issue, maybe the error message could at least provide me with enough information to manually set the permissions (in case that actually solves the issue).

nix-env --version output

nix-env (Nix) 2.8.1

Additional context

This is a single-user Nix install on Arch Linux. There are issues with a similar error message for Darwin installs: #3435 #6667. Re-installing Nix on my system to "solve" the problem is a non-starter.

[tomberek]

Likely needs better "--repair" options? Otherwise I don't know how to address this problem.