Cross-process advisory lock serialising privileged (sudo) filesystem
mutations. nextest runs each test in its own OS process, so an
in-process Mutex cannot prevent concurrent test processes from racing
on a real, shared system path (e.g. /etc/docker/daemon.json); this
lock closes that window for both tests and real concurrent invocations.
Acquires the cross-process advisory lock serializing privileged (sudo)
filesystem mutations. Shared beyond this module by other privileged
writes (e.g. the self-install binary copy in self_install.rs) that
need to serialize against concurrent sudo-driven writes.