Restore the Android Threads workaround for Qt 6
This does no longer affect regular projects with current Qt 6, but it does break the rare CXX-only one again now, like e.g. seen in kquickimageditor.
This does no longer affect regular projects with current Qt 6, but it does break the rare CXX-only one again now, like e.g. seen in kquickimageditor.