message: [POSIX] Replace assert with llvm_unreachable(). NFCI.
diff: @@ -43,7 +43,7 @@ Status HostThreadPosix::Cancel() {
  if (IsJoinable()) {
  #ifndef __ANDROID__
  #ifndef __FreeBSD__
  - assert(false && "someone is calling HostThread::Cancel()");
  + llvm_unreachable("someone is calling HostThread::Cancel()");
  #endif
  int err = ::pthread_cancel(m_thread);
  error.SetError(err, eErrorTypePOSIX);
  