cc -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations spawn/POSIX_SPAWN_SETSCHEDULER.c -o spawn/POSIX_SPAWN_SETSCHEDULER -D_POSIX_C_SOURCE=202405L  -lm -lpthread  -liconv
spawn/POSIX_SPAWN_SETSCHEDULER.c:3:17: error: use of undeclared identifier 'POSIX_SPAWN_SETSCHEDULER'
    3 | int const foo = POSIX_SPAWN_SETSCHEDULER;
      |                 ^
1 error generated.