message: Fix broken build: change switch cast to use llvm_unreachable.
diff: @@ -227,7 +227,7 @@ void TerminatorInst::eraseFromBlock() {
  MutableArrayRef<BBDestination> TerminatorInst::getDestinations() {
  switch (getKind()) {
  case Kind::Operation:
  - assert(0 && "not a terminator");
  + llvm_unreachable("not a terminator");
  case Kind::Branch:
  return cast<BranchInst>(this)->getDestinations();
  case Kind::CondBranch:
  