Hello! We, at Gentoo, work on improving the state of NGINX ecosystem. As part of our efforts, I have been working on better supporting your module.

Getting straight to the point. Your config check checks whether clock_gettime() is available, additionally including the sched.h header.

This fails, because, according to POSIX and GNU, the clock_gettime() function is provided by time.h, not sched.h.

Thus, the line

should be changed to

ngx_feature_incs="#include <time.h>"

to check for clock_gettime() properly. I will follow this issue with a PR fixing this.