...instead of just for i686-linux.
Without a --with-pcap= configure flag, the build system tries to
auto-detect the backend by poking in /dev, /usr/include etc... In the
pure nix world, this auto-detection fails. (Good, we don't want host
details to leak into the build.)
The end result of this (failed) auto-detection; no packet capture
possible:
$ sudo tcpdump -i wlp2s0
tcpdump: live packet capture not supported on this system
This fixes the above issue on 64-bit linux systems, and probably other
architectures supported by linux.