--- uncontended: execs the evaluator with the arguments
--- exit status propagates
--- missing lock file refuses to evaluate
--- second evaluation waits for the holder, then proceeds
--- holder killed: the lock goes with it
/build/.attr-0l2nkwhif96f51f4amnlf414lhl4rv9vh8iffyp431v6s28gsr90: line 75:    58 Killed                     HOLD_UNTIL=run/never nix-eval-jobs doomed > /dev/null 2>&1
--- sandboxed waiter (nixbot's case): read-only lock, holder invisible
--- sandboxed holder: an outside waiter names it