[clang] [Clang] Correct handling of negative and out-of-bounds indices (PR #71877)

[Bill Wendling via cfe-commits]

bwendling wrote:

> For the test cases, I wonder if it might be good to add __bdos() calls with type 0 as well. The results should always be the same, but we do want to check for that. i.e.:
> 
> ` p->array[index] = __builtin_dynamic_object_size(&p->count, 0);`

I can do that in a separate commit. It'll be nicer than crowding changes to the test case in here. :-)

https://github.com/llvm/llvm-project/pull/71877