Auto-detect build directory to successfully run unit tests

[pdschubert]

Automatically detect the build directory (for the unit tests) to successfully run the unit in more advanced setups.

[MMory]

@fabianbs96 @pdschubert this should have been fixed recently, right?

[fabianbs96]

If there are problems with that, they will automatically get fixed by #516

[MMory]

This should be fixed by a recent PR, am I correct @fabianbs96 ?

[fabianbs96]

@MMory, yes that is part of #673

[MMory]

fixed with #673