[seccomp] allow sendmsg

moving logging to its own process

accept4 -> accept accept4(2) isn't part of any standard (even though it'll be part in the future) and raises warnings on some linux distro. Moreover, we don't have thread that may fork at any time, so doing a mark_nonblock after isn't a big deal.

use fatal instead of err/fprintf+exit fatal logs to the correct place, err only on stderr.

fix compilation on OSes without sandbox

[seccomp] allow newfstatat and gettimeofday these are required to run on arch linux (at least)

[seccomp] epoll_wait(2) isn't available on every arch

allow epoll_wait fedora 33 issue an epoll_wait instead of pwait.

allow sigreturn and sigaction on linux

fix seccomp for the new event loop add/remove syscalls from the BPF filter and move sandbox() after libevent initialisation

don't include err.h, gmid.h (via config.h) does that

[seccomp] allow getrandom

we don't need unveil "x" in listener not a big deal, since the pledge prohibits us to exec, but nevertheless.

[seccomp] allow fcntl F_SETFD musl does a F_SETFD in its fdopendir

fix date