[MSAN] adjust Posix/timer.cpp

[kda]

Summary

follow up to 0a4dec6cc2bf.
add unsupported for s390 (SEGV)
restore line that s390 complains, so following asserts work.

[pirama]

Looks like this assert is broken? https://reviews.llvm.org/B153417 and https://reviews.llvm.org/B153416 are some early indications.

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

 // RUN: %clangxx -O0 -g %s -o %t && %run %t
 // UNSUPPORTED: darwin
+// FIXME: SEGV - API mismatch?
+// UNSUPPORTED: s390
 #include <assert.h>
 #include <signal.h>
 #include <stdio.h>
 #include <string.h>
 #include <time.h>
 
 int main(int argc, char **argv) {
   struct sigevent sev {};
   sev.sigev_notify = SIGEV_NONE;
   timer_t timerid;
   assert(timer_create(CLOCK_REALTIME, &sev, &timerid) == 0);
 
   struct itimerspec new_value {};
   new_value.it_value.tv_sec = 10;
   new_value.it_value.tv_nsec = 1000000;
   new_value.it_interval.tv_sec = new_value.it_value.tv_sec;
   new_value.it_interval.tv_nsec = new_value.it_value.tv_nsec;
 
+  assert(timer_settime(timerid, 0, &new_value, nullptr) == 0);
+
   struct itimerspec old_value;
   assert(timer_settime(timerid, 0, &new_value, &old_value) == 0);
   assert(old_value.it_interval.tv_sec == new_value.it_interval.tv_sec);
   assert(old_value.it_interval.tv_nsec == new_value.it_interval.tv_nsec);
   assert(old_value.it_value.tv_sec <= new_value.it_value.tv_sec);
   assert(old_value.it_value.tv_nsec <= new_value.it_value.tv_nsec);
 
   struct itimerspec curr_value;