For what it's worth, I rebased my branch so that the CI now passes.
The new commit with the patch is: https://salsa.debian.org/arnaudr/git-buildpackage/-/commit/8f10840587e05b27ee43fbff10480ef2734805bb
BTW, please tell me if there's a better workflow than having a fork on Salsa, in order to contribute to gbp.
Thanks! -- Arnaud Rebillout / Offensive Security / Kali Linux Developer