wg-quick fails with systemd resolvconf compatibility shim

[Andrei Borzenkov]

systemd resolvectl supports resolvconf compatibility mode when invoked 
as resolvconf. Ubuntu 24.04 apparently no more provides the real recolvconf:

bor at bor-Latitude-E5450:~/tmp$ dpkg-query -S /usr/sbin/resolvconf
systemd-resolved: /usr/sbin/resolvconf

This version requires the real interface and fails with wg-quick hack:

bor at bor-Latitude-E5450:~/tmp$ sudo wg-quick up ./wg0.conf
[#] ip link add wg0 type wireguard
[#] wg setconf wg0 /dev/fd/63
[#] ip -4 address add 192.168.6.160/32 dev wg0
[#] ip link set mtu 1420 up dev wg0
[#] resolvconf -a tun.wg0 -m 0 -x
Failed to resolve interface "tun.wg0": No such device
[#] ip link delete dev wg0
bor at bor-Latitude-E5450:~/tmp$

So, wg-quick became unusable on Ubuntu. It worked fine in Ubuntu 22.04.