error: could not find native static library `bpf`

[KarstenB]

When using the library, the bpf library could not be found. This is most likely caused by a missing call to make in the build.rs.
Something like this should do the trick (untested):

    let status = process::Command::new("make")
        .current_dir(& libbpf_dir)
        .status()
        .expect("could not execute make");