The following is a questing from the Debian pkg-bitcoin-dev group and I am interested too:
If you are familiar, could you explain this? Why should we not be
using system libusb?
- Added yet more warnings suggesting not to use the system libusb in configure.
Debian Jessie and Unstable (SID) libusb
libusb-1.0-0 (2:1.0.19-1)