POSIX specification: https://pubs.opengroup.org/onlinepubs/009695399/functions/usleep.html
Gnulib module: usleep
Portability problems fixed by Gnulib:
usleeprejects attempts to sleep longer than 1 second, as allowed by POSIX: NetBSD 9.0, mingw.
Portability problems not fixed by Gnulib:
usleepfunction may interfere with the program’s use of the
SIGALRMsignal. On Linux, it doesn’t; on other platforms, it may.