always setup logging, dump whatever its logged

[cre4ture]

draft 2 for #6284, alternative for #6313

The main idea here is, that the logs are not part of the stable code-base. They would always be removed when debuggin is done. This way, there is no explicit activation mechanism needed and the test-framework can always specify the logfile-path via environmental variable. It will check after execution if the logfile was written to and then dumps the content.

[github-actions[bot]]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)