[ObjC] Use os_unfair_lock instead of dispatch_semaphore_t.
The minOS version is high enough it can be used, and it avoids the long standing issue for priority inversion dependent on what callers did with threading/queues.
T
Thomas Van Lenten committed
d7d780ce751b08c5d62fb80e91ce88ce65be7ba3
Parent: 2bed343