iOS: Investigate Qt6 crash & update afterwards

[hoffie]

Finally found out (again) how to view iOS crash logs. You need macOS and The console App. I think that's the error:

We probably need to change the application class. Or maybe https://forum.qt.io/topic/82102/can-t-create-qapplication-for-ios-using-cmake-build

Originally posted by @ann0see in https://github.com/jamulussoftware/jamulus/issues/2300#issuecomment-1172693513

(Also see further investigation by @pljones in that ticket)

Original commit (including a relevant workaround) for reference: de632f4a9f84200f72ace34a101770c5b7a48fcf

[hoffie]

See https://github.com/jamulussoftware/jamulus/pull/2625#issuecomment-1275690542:

QMAKE_LFLAGS += -Wl,-e,_qt_main_wrapper

Thanks to @danryu.

[pljones]

@hoffie any progress on this?

[ann0see]

I think the GUI gets messed up with QT 6.