message: Fix static assertion in AttributeDetail.h
  llvm::maskTrailingOnes<char> runs into a static assertion on the type not being
  unsigned.  Use `unsigned char` instead of `char`.
diff: @@ -469,7 +469,7 @@ struct DenseElementsAttributeStorage : public AttributeStorage {
  if (splatValue && numOddElements != 0) {
  // Check that all bits are set in the last value.
  char lastElt = splatData.back();
  - if (lastElt != llvm::maskTrailingOnes<char>(numOddElements))
  + if (lastElt != llvm::maskTrailingOnes<unsigned char>(numOddElements))
  return KeyTy(ty, data, llvm::hash_value(data));
  // If this is the only element, the data is known to be a splat.
  