cc -pthread  -Wall -Wextra -Werror -Wno-error=deprecated -Wno-error=deprecated-declarations stdlib/O_SYNC.c -o stdlib/O_SYNC -D_POSIX_C_SOURCE=202405L  -lm -lpthread  -liconv
stdlib/O_SYNC.c:2:17: error: use of undeclared identifier 'O_SYNC'
    2 | int const foo = O_SYNC;
      |                 ^
1 error generated.