Further versions broke the build system,
see 18443d861e.
With 5.15.1 it basically works again but deployment with androiddeployqt
does not produce runnable APKs. Qt now has gained support for invoking
androiddeployqt within CMake. Using their official support instead of my
own helper might have worked but it could not cope with the fact that I
had multiple targets in my CMake project and was therefore useless in my
case.
So let's ditch Qt 5 on Android and give Qt 6 another chance at some
point.
