iOS support is broken for Qt6

1. QBS_ASSERT(!"QByteArray is not a valid type for JS variant", return JS_UNDEFINED);
in qbs::Internal::PropertyList::jsToObject; fixed in the upstream
2. compiledqml example is broken (pre files do not replace $$[QT_INSTALL_QML] in qml; both release and debug objects are linked in the app causing "duplicate symbol" error)
3. in Qt 6.2.3 prf files are broken - the qt install dir is not replaced via a variable; fixed in the upstream (but another problem occurs in 6.5.0)
4. plugins prfs now have _debug suffix similar to Windows; fixed in the upstream