[BUGFIX] runTests.sh: Fix macos user detection

Check for user in /etc/passwd, if it does not exist create
a temporary passwd to get values from.

Resolves: #93372
Releases: master, 10.4, 9.5
Change-Id: I60c9d2a10a0da155354546d57c823961bc39f014
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67539


Tested-by: Jochen <rothjochen@gmail.com>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Jochen <rothjochen@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>