bug#55628: debug-timer-check fails on macOS 11.6.6

[Mattias Engdegård]

25 maj 2022 kl. 15.05 skrev Mattias Engdegård <mattiase@acm.org>:

> More digging shows that set_alarm always sets the interval timer to at least 
> 1 ms in the future even if the timer has expired.

In fact it was even worse than that: because of a second bug, the timer was 
then immediately reset to at least 1 s in the future. The proposed patch fixes 
both flaws.

Good to have a test for it -- maybe it should always be enabled, not just with 
enable-checking? People don't always reconfigure, rebuild and re-run the tests 
with enable-checking, nor do any of the build bots.