I'm getting a couple of warnings trying to build this on Arch:

src/uxn11.c:6:1: error: C++ style comments are not allowed in ISO C90
   6 | //#include <sys/timerfd.h>
     | ^
src/uxn11.c:6:1: note: (this will be reported only once per input file)
src/uxn11.c: In function ‘main’:
src/uxn11.c:250:17: warning: implicit declaration of function
‘usleep’; did you mean ‘sleep’? [-Wimplicit-function-declarati
on]
 250 |                 usleep(16666); // <--- INSTEAD OF TIMERFD
     |                 ^~~~~~
     |                 sleep