d/extra/prepare-commit-package.sh: Improve verbosity, specificity.

22 jobs for debian/bullseye in 7 minutes and 47 seconds (queued for 3 seconds)
latest
Name Stage Failure
failed
reuse Build
* Unused licenses:
* Used licenses: Apache-2.0, BSD-2-Clause, BSD-3-Clause, BSL-1.0, CC-BY-4.0, CC0-1.0, LicenseRef-Khronos-Free-Use-License-for-Software-and-Documentation, MIT, Unlicense
* Read errors: 0
* Files with copyright information: 966 / 998
* Files with license information: 966 / 998

Unfortunately, your project is not compliant with version 3.0 of the REUSE Specification :-(
Cleaning up file based variables
ERROR: Job failed: exit code 1