Comment 13 for bug 1974177

I've opened an MR [1] with upstream's sbuild to fix the umask difference (and traced the difference in umasks to Debian's common-session PAM configuration lacking pam_umask.so).

Attaching an updated debdiff with the isolation-machine change (this has also been uploaded to the aforementioned sbuild PPA).

[1]: https://salsa.debian.org/debian/sbuild/-/merge_requests/24