[llvm] [BOLT][AArch64] Check Last Element Instead of Returning `nullptr` in `lookupStubFromGroup` (PR #114015)

[Paschalis Mpeis via llvm-commits]

https://github.com/paschalis-mpeis commented:

At a quick glance this seems to be a valid edge case.
It happens when all candidates (sorted stubs) are smaller than the input DotAddress?

In theory, there can be a pathological case where DotAddresses happen to always be bigger during lookups, causing the creation of new stubs each time.

Have you encountered any such extremes? And can you come up with a test case?

https://github.com/llvm/llvm-project/pull/114015