Fix warning about ASCII cast in calling QString::contains

(cherry picked from commit 4671c273edb87e55436dd3bf0b371267c5e34ff7)

src/declarative/debugger/qdeclarativedebugserver.cpp

@@ -184,7 +184,7 @@ QDeclarativeDebugServer *QDeclarativeDebugServer::instance()
                 int separatorIndex = appD->qmljsDebugArgumentsString().indexOf(QLatin1Char(','));
                 port = appD->qmljsDebugArgumentsString().mid(5, separatorIndex - 5).toInt(&ok);
                 pluginName = QLatin1String("qmldbg_tcp");
-            } else if (appD->qmljsDebugArgumentsString().contains("ost")) {
+            } else if (appD->qmljsDebugArgumentsString().contains(QLatin1String("ost"))) {
                 pluginName = QLatin1String("qmldbg_ost");
                 ok = true;
             }