[Development] Build system for Qt 6

[Kevin Kofler]

Christian Gagneraud wrote:
> Fairly interesting indeed, and very surprising too, this WIN32/Android
> stuff was fixed last week, i didn't invent it.
> Maybe, we ran into bad luck.

The bug you ran to only hits you when ALL 3 of the following conditions are 
satisfied:
1. Windows build host,
2. non-Windows build target, AND
3. using Qt autogen.

Condition 3 is probably the one the Google developers never exercised when 
testing their Android Studio NDK support on Windows. I doubt they test with 
Qt, unfortunately.

        Kevin Kofler