cc -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations threads/ONCE_FLAG_INIT.c -o threads/ONCE_FLAG_INIT -D_POSIX_C_SOURCE=202405L  -lm -lpthread  -liconv
threads/ONCE_FLAG_INIT.c:1:10: fatal error: 'threads.h' file not found
    1 | #include <threads.h>
      |          ^~~~~~~~~~~
1 error generated.