Doesn't build with libbpf 1.0+
The failure looks familiar, but libbpf is now at a newer version (1.0.0/1.0.1).
In file included from libknot/xdp/xdp.c:32:
./libknot/xdp/bpf-user.h:28:10: fatal error: bpf/xsk.h: No such file or directory
28 | #include <bpf/xsk.h>
| ^~~~~~~~~~~
compilation terminated.