fix leak in Posix/timer.ccp

[kda]

Summary

Fix leak interoduced in c2aab0d3808b.

compiler-rt/test/sanitizer_common/TestCases/Posix/timer.cpp

int main(int argc, char **argv) {
 
   struct itimerspec curr_value;
   assert(timer_gettime(timerid, &curr_value) == 0);
   assert(curr_value.it_interval.tv_sec == new_value.it_interval.tv_sec);
   assert(curr_value.it_interval.tv_nsec == new_value.it_interval.tv_nsec);
   assert(curr_value.it_value.tv_sec <= new_value.it_value.tv_sec);
   assert(curr_value.it_value.tv_nsec <= new_value.it_value.tv_nsec);
 
+  assert(timer_delete(timerid) == 0);
+
   return 0;
 }