[llvm] [TableGen] Add check for number of intrinsic return values (PR #107326)

[Rahul Joshi via llvm-commits]

jurahul wrote:

Linux build failure in lldb test seems unrelated. Also, currently without this check, we hit the following assert:

llvm-tblgen: /home/rjoshi/upstream_llvm/llvm-project/llvm/include/llvm/Support/Casting.h:578: decltype(auto) llvm::cast(From *) [To = llvm::ListInit, From = const llvm::Init]: Assertion `isa<To>(Val) && "cast<Ty>() argument of incompatible type!"' failed.

That's because in :

```
  list<list<int>> TypeSig = !listconcat(
    [IIT_RetNumbers[!size(RetTypes)]],

```

There is OOB indexing into the IIT_RetNumbers list, resulting in an unresolved record or something like that.

https://github.com/llvm/llvm-project/pull/107326