QMTest cannot have prerequisites from other subdirectories
If one adds a prerequisite on a test from another subdirectory
<argument name="prerequisites"><set>
<tuple><text>Hlt1Conf.persistency.allen_mdf_write</text><enumeral>PASS</enumeral></tuple>
</set></argument>
the current subdirectory is prepended giving the error
ERROR: prerequisite Hlt2Conf.Hlt1Conf.persistency.allen_mdf_write [...] not found
It appears that the problem is around this line: https://gitlab.cern.ch/gaudi/Gaudi/-/blob/b65f1d453f28a1b7951026b391aa704f9b91681d/cmake/extract_qmtest_metadata.py#L105
Thanks to @nskidmor for reporting.