bug#50264: ca-certificate-bundle fails to build

[Lars-Dominik Braun]

Hi Leo,

> I wonder if the problem began after the introduction of
> bordeaux.guix.gnu.org, and if everyone who experiences the bug is using
> both substitute servers.
I started the Guix daemon with only the CI substitute server enabled
explicitly, disabled local discovery, ran a `guix gc` and tried again. It
still fails with exactly the same issue.

Lars