As it turns out older versions of the Android NDK have mntent.h but not
a complete implementation. If it did work it would most likely give the
wrong results on Android anyway.
This commit enables the UNIX drive discovery only for X11
We also missed '/run/media' (default for gnome desktops) in the list of
places to look for 'drives' on Linux. Add that to the list also.
This fixes#11270