compile fails in gcc14

[gilcu3]

There seems to be a change in gcc-14 on linux that makes the build fail:

gcc -g -std=c11 -O3 -fomit-frame-pointer -Wall  -I.  -c -o threadpool.o threadpool.c
threadpool.c: In function ‘tpool_stop’:
threadpool.c:132:13: error: implicit declaration of function ‘usleep’ [-Wimplicit-function-declaration]
  132 |             usleep(1);
      |             ^~~~~~
make: *** [Makefile:120: threadpool.o] Error 1

With gcc-13 the same command works.