Use non Qt 5.10 method of starting a detached process

src/util/streamlink.cpp

@@ -150,11 +150,14 @@ void OpenStreamlink(const QString &channelURL, const QString &quality, QStringLi
         arguments << quality;
     }
 
+    /*
+    // This only works in Qt 5.10 and above
     auto p = createStreamlinkProcess();
-
     p->setArguments(arguments);
-
     bool res = p->startDetached();
+    */
+
+    bool res = QProcess::startDetached(getStreamlinkProgram(), arguments);
 
     if (!res) {
         showStreamlinkNotFoundError();