This allows using a userspace program, pasta, to handle comms between the build sandbox, and the outside world; allowing for full isolation including the network namespace, closing the "fixed-output derivation talks to the host over an abstract domain socket" hole for good. Fixes CVE-2025-46416. Co-Authored-By: Puck Meerburg <puck@puckipedia.com> Change-Id: Ifd499b7dbb3784600a6e842fede65fc031ff9f15