Implement networking ioctls for launchd

[LubosD]

launchd tries to setup networking - loopback specifically (lo0), throws assertion failures currently.

ioctls:

• SIOCGIFFLAGS
• SIOCSIFFLAGS
• SIOCAIFADDR
• SIOCAIFADDR_IN6

[facekapow]

Given that we don't want to have separate networking from the host, I'd say that the dummy ioctls are enough.

[bugaevc]

At some point we wanted an option to toggle between "share networking with the host" and "have a Darling container run in its own network namespace". Not sure if we still want that though.

[LubosD]

It is definitely interesting for Docker usage, because Docker defaults to having distinct network hosts for containers.

[bugaevc]

But in case of Docker we also would want for the Darling container to share networking with "the host" (i.e. the Docker container), not to create another nested namespace with its own networking.