Update libcxx sleep_for.signal.pass to use timer_settime instead of setitimer

Author: biabbas

libcxx/test/libcxx/thread/thread.threads/thread.thread.this/sleep_for.signals.pass.cpp

@@ -44,13 +44,21 @@ int main(int, char**)
   ec = sigaction(SIGALRM, &action, nullptr);
   assert(!ec);
 
-  struct itimerval it;
-  std::memset(&it, 0, sizeof(itimerval));
+  timer_t timer_id = 0;
+  struct sigevent _sev;
+  _sev.sigev_signo           = SIGALRM;
+  _sev.sigev_notify          = SIGEV_SIGNAL;
+  _sev.sigev_value.sival_ptr = &timer_id;
+  ec                         = timer_create(CLOCK_REALTIME, &_sev, &timer_id);
+  assert(!ec);
+
+  struct itimerspec it;
+  std::memset(&it, 0, sizeof(itimerspec));
   it.it_value.tv_sec = 0;
-  it.it_value.tv_usec = 250000;
+  it.it_value.tv_nsec = 250000000;
   // This will result in a SIGALRM getting fired resulting in the nanosleep
   // inside sleep_for getting EINTR.
-  ec = setitimer(ITIMER_REAL, &it, nullptr);
+  ec = timer_settime(timer_id, 0, &it, nullptr);
   assert(!ec);
 
   typedef std::chrono::system_clock Clock;