[Qbs] Install/Depends resolution changed from qbs 1.12.2 to qbs 1.13.0?

[Richard Weickelt]

> Oh yeah, it has been an unsatisfying surprise that default installation
> prefix changed from empty string to "usr/local/" on Linux. All builds
> are broken, all scripts working on the results are broken. Not
> hardcoding is not an option when it comes to CI integration etc.
> 
> Next time I will be happy if such a change is announced in capital
> letters.

This was also an unpleasant surprise for me. Note that
https://doc.qt.io/qbs/qml-qbsmodules-qbs.html#installPrefix-prop does not
reflect this change. Thus, instead of going over the docs, I'd rather like
to set installPrefix back to undefined on all platforms for Qbs 1.13.1.

Anything that speaks against that?

Richard