Exclude other filesystems on counts.

without -x if you have mounted e.g. sdcard or something to a directory
it counts that into the space which is not right.

[disk] Do not follow to other filesystems. Contributes to JB#40595

Signed-off-by: Marko Saukko <marko.saukko@jolla.com>

src/diskusage_impl.cpp

@@ -68,7 +68,7 @@ quint64 DiskUsageWorker::calculateSize(QString directory, QString *expandedPath,
     }
 
     QProcess du;
-    du.start("du", QStringList() << "-sb" << directory, QIODevice::ReadOnly);
+    du.start("du", QStringList() << "-sbx" << directory, QIODevice::ReadOnly);
     du.waitForFinished();
     if (du.exitStatus() != QProcess::NormalExit) {
         qWarning() << "Could not determine size of:" << directory;