Fix warnings on wasi

[nobu]

../src/thread.c:4565:1: warning: unused function 'consume_communication_pipe' [-Wunused-function]
consume_communication_pipe(int fd)
^
In file included from ../src/thread.c:263:
../src/thread_none.c:50:1: warning: unused function 'rb_thread_sched_destroy' [-Wunused-function]
rb_thread_sched_destroy(struct rb_thread_sched *sched)
^
../src/thread_none.c:275:1: warning: unused function 'th_has_dedicated_nt' [-Wunused-function]
th_has_dedicated_nt(const rb_thread_t *th)
^
../src/thread.c:1664:1: warning: unused function 'waitfd_to_waiting_flag' [-Wunused-function]
waitfd_to_waiting_flag(int wfd_event)
^
../src/time.c:2349:35: warning: incompatible pointer types passing 'wideval_t *' (aka 'unsigned long long *') to parameter of type 'VALUE *' (aka 'unsigned long *') [-Wincompatible-pointer-types]
    split_second(tobj->timew, &t, &s);
                                  ^~
../src/time.c:616:58: note: passing argument to parameter 'subsecx_p' here
split_second(wideval_t timew, wideval_t *timew_p, VALUE *subsecx_p)
                                                         ^