Fix Qt 5.6+ main() support for iOS and tvOS
Fix Qt 5.6+ main() support for iOS and tvOS

Don't link to qtmn in Qt 5.6; in that version it has been superseded by
setting the entry point to _qt_main_wrapper.

Change-Id: I9941f7347ffbe530550430ce93e1867edbc0985a
Reviewed-by: Christian Kandeler <3aa99dcdd3f0cac61fb81c2a11771c0cc2497607@qt.io>

qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qt-labs/qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs,qt-labs/qbs,qt-labs/qbs,qtproject/qt-labs-qbs,qtproject/qt-labs-qbs