iOS: qSetMessagePattern() does not affect the output from qDebug et al.

In qDefaultMessageHandler(), on all other OSes and logging systems we call a <system>_message_handler() function, and those call qFormatLogMessage. But on iOS, qFormatLogMessage() isn't being called: we just directly call AppleUnifiedLogger::messageHandler(type, context, message). So, the output of the app in XCode doesn't have the information which is specified in qSetMessagePattern(). I expected that I could do

    qSetMessagePattern("[%{time process} %{if-debug}D%{endif}%{if-warning}W%{endif}%{if-critical}C%{endif}%{if-fatal}F%{endif}] %{category} %{function} - %{message}");

in main.cpp before creating the QGuiApplication, since setting env variables probably doesn't work. (On desktop OSes, I always set the QT_MESSAGE_PATTERN variable. The calling function %{function} is actually what I need the most though, since the xcode output does have some of the other stuff, like timestamp.)

QTBUG-69450 is the opposite problem, on Android: it was repeating this information. At least the patch helped me figure out where to look.

Maybe AppleUnifiedLogger outputs the type and context somewhere, but not in the XCode output pane.