Osmocom applications typically use libosmocore select.[ch] event loop
code as their main event dispatch mechanism. When they want to deal
with libusb in a non-blocking/asynchronous way, they need to integrate
libusb into that select().
The new libosmousb is doing exactly that: Providing a shared utility
library for Osmocom programs that wish to use libusb. This is useful
for example in simtrace2 host utilitie as well as osmo-e1d.