[FOLLOWUP][TASK] Clean up unit tests on Windows

Use OS independent temp directory.

Change-Id: Idb6f0a0d9f5666ca84ec10d9a342bf29c0571068
Resolves: #75388
Releases: master
Reviewed-on: https://review.typo3.org/47536


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Stephan Großberndt <stephan@grossberndt.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>