If Rockbox Utility has no configuration file on the machine updateSettings()
will overwrite the global cache folder settings with an empty string before the
value is set properly by the user confirming the configuration dialog. QDir()
getting an empty string will result in the current working directory getting
used, and thus the temporary files ending up there.
On Windows most users are unlikely to have noticed this since running the
executable from within the distribution zip file will make Windows execute it
in the systems temporary path.
Change-Id: I7724a82af403955786798c7380198086837e128f
280a0eb27e