[Development] moc output from non-local tool build

[Marius Kittler]

Am Dienstag, 14. September 2021, 09:51:21 CEST schrieb Joerg Bornemann:
> The maintenance burden is next level. This would mean to keep all
> internal API that's used in lib/cmake compatible. Apparently forward and
> backward if I read your requirements correctly.
> 

I'm afraid that's the next challenge, indeed. I've recently tried to use host 
Qt 6.2 (beta) with Qt 6.1.3 targeting mingw-w64 and it also broke because it 
couldn't find some CMake functions. One would have expected that this isn't a 
problem because my host Qt was newer but apparently its configuration files 
are not self-contained and try to call helper functions from the target Qt 
instead of "staying in the host world". But would be "staying in the host 
world" problematic? I suppose it comes with the challenge of avoiding name 
clashes between the host and target worlds but I guess it should be doable.