Interesting choice of syscalls: https://github.com/ffwff/lilith/blob/master/userspace/librar.... No fork; instead it seems to implement spawnv.
While it is possible to create and manage some rules, it is simpler not to fork at all.
I guess I should reword it :/
https://fuchsia.googlesource.com/docs/+/refs/changes/56/1013...