Bail on autodetecting USB and revert to a compile-time flag.
Bail on autodetecting USB and revert to a compile-time flag.

I thought the auto-detect was more stable than it actually is, so I've marked
teh current state of the art in the usbdetect branch and moved back to using a
compile-time flag in master.

openxc/vi-firmware,mgiannikouris/vi-firmware,ene-ilies/vi-firmware,mgiannikouris/vi-firmware,openxc/vi-firmware,openxc/vi-firmware,openxc/vi-firmware,mgiannikouris/vi-firmware,ene-ilies/vi-firmware,ene-ilies/vi-firmware,ene-ilies/vi-firmware,mgiannikouris/vi-firmware