I'm trying to build @mastahyeti 's U2F example, but it looks like the latest release pre-dates the example by nearly a year. It might be nice to post a new release at some point so that the U2F example works out-of-the-box.

Also, for future people that are looking to build that example note that you need another compilation flag:

gcc u2f.c -o virtual_u2f -framework IOKit -framework CoreFoundation