[osx] use CLOCK_REALTIME for init_timeout

[connorjclark]

#1511 changed osx clocks to use CLOCK_MONOTONIC_RAW, but that is an issue for the timeout structure because pthread expects an absolute system time. This resulted in timed event calls returning instantly.

See https://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_cond_timedwait.html#:~:text=Timed%20Wait%20Semantics

[SiegeLord]

I couldn't reproduce the instant timeouts (I used ex_timedwait, suspended the system, resumed and then saw if the timeouts were affected... they were not), but your reasoning seems reasonable.

[connorjclark]

Perhaps by attaching a debugger you could get the monotonic raw clock to drift from system clock... I think I was using a debugger. It could also be implementation-defined whether the clocks even align on process start (just guessing).

[SiegeLord]

I tried the debugger, but still no luck. I don't mind merging this if it helps on your system though.