QLogging: switch the systemd/journald sink to unformatted mode

The extra information is already stored in the journal metadata anyway,
so there's no need to duplicate it. This matches the Apple Unified
Logger output now.

For most people, the visible difference will be that the category name
is not included in the plain "journalctl" output.

 Aug 22 21:25:43 tjmaciei-mobl5 akonadi_imap_resource[4948]: org.kde.pim.kimap: Connection to server lost  QAbstractSocket::HostNotFoundError
 Aug 22 21:27:17 tjmaciei-mobl5 kwin_x11[3376]: kwin_core: XCB error: 3 (BadWindow), sequence: 41165, resource id: 29363347, major code: 129 (SHAPE), minor code:>

journalctl does not make it easy to show extra fields, but it's there
and can be retrieved with -o verbose.

[ChangeLog][QtCore][Logging] The Qt logging framework (qDebug/qWarning/etc)
will now only send the plain, unformatted message to systemd's journald,
if this backend is enabled. The category and other fields are sent via
metadata to journald, so they can be filtered on and retrieved using
journalctl. This matches what Qt does for the Apple Logging support and
does not apply when Qt is using syslog or stderr to communicate with
journald.

Change-Id: Ifa1111900d6945ea8e05fffd177de8f47d74ba60
Reviewed-by: Kai Köhne <[email protected]>

src/corelib/global/qlogging.cpp

@@ -1796,7 +1796,7 @@ static bool slog2_default_handler(QtMsgType type, const QMessageLogContext &,
 #if QT_CONFIG(journald)
 static bool systemd_default_message_handler(QtMsgType type,
                                             const QMessageLogContext &context,
-                                            const QString &formattedMessage)
+                                            const QString &message)
 {
     if (shouldLogToStderr())
         return false; // Leave logging up to stderr handler
@@ -1820,7 +1820,7 @@ static bool systemd_default_message_handler(QtMsgType type,
         break;
     }
 
-    sd_journal_send("MESSAGE=%s",     formattedMessage.toUtf8().constData(),
+    sd_journal_send("MESSAGE=%s",     message.toUtf8().constData(),
                     "PRIORITY=%i",    priority,
                     "CODE_FUNC=%s",   context.function ? context.function : "unknown",
                     "CODE_LINE=%d",   context.line,
@@ -2002,7 +2002,7 @@ static constexpr SystemMessageSink systemMessageSink = {
 #elif QT_CONFIG(slog2)
         slog2_default_handler
 #elif QT_CONFIG(journald)
-        systemd_default_message_handler
+        systemd_default_message_handler, true
 #elif QT_CONFIG(syslog)
         syslog_default_message_handler
 #elif defined(Q_OS_ANDROID)