lock port for concurrent
dolock creates a lock named
open(2). If the lock is already held, it will display one single wait
message on stderr, sleep and retry until satisfaction.
If necessary, creates the lock directory, using
-m mode as a mode argument or
the default if that option is not specified, and
group as the group owner if that option is
This implements a locking mechanism for ports building, see ‘LOCK INFRASTRUCTURE’ in ports(7) for details. See also dpb(1) for a complementary lock infrastructure when using dpb.