message: Fix build error by using isa<llvm::ScalableVectorType> instead of isScalable
diff: @@ -489,7 +489,7 @@ public:
  auto ofs_ty = llvm::IntegerType::get(i.getContext(), 64);
  if (auto opvty = dyn_cast<llvm::VectorType>(opty)) {
  - assert(!opvty->isScalable());
  + assert(!isa<llvm::ScalableVectorType>(opvty));
  vector<llvm::Constant *> offsets;
  for (unsigned i = 0; i < opvty->getElementCount().Min; ++i) {
  