[BasicIndexingBenchmark] Optionally keep DB file to allow further analysis
The created DB can then be used and examined with e.g.
$> export BALOO_DB_PATH=...
$> balooctl indexSize
$> baloosearch foo
The created DB can then be used and examined with e.g.
$> export BALOO_DB_PATH=...
$> balooctl indexSize
$> baloosearch foo