[Development] Switch the main "Qt Build System"

[Kai Köhne]

> -----Ursprüngliche Nachricht-----
> Von: Development <development-bounces at qt-project.org> Im Auftrag von
> [...]
> To build autotests, -DFEATURE_developer_build=ON will do that right?  And
> there are also BUILD_TESTING and QT_NO_MAKE_TESTS so what’s the
> relationship?

It's currently the same as with qt 5:

 *  FEATURE_developer_build does (among other things) enable tests (BUILD_TESTING) by default, for most platforms.
 * QT_NO_MAKE_TESTS defines whether a default build will build the tests; the default is OFF (so a mere ninja/jom ... will build all tests)

Question is whether this is actually what we want in Qt 6, see  https://bugreports.qt.io/browse/QTBUG-84471 for some discussion.

Regards

Kai