[llvm] [Object][GOFF] Recognize RLD and LEN records (PR #207118)

[Amy Kwan via llvm-commits]

amy-kwan wrote:

> My point was more that is this patch sufficient to handle all possible cases? `llvm_unreachable` should only be used if it is impossible programmatically to hit the code, so while this change is an improvement, if another value (perhaps a value that isn't a valid record type) were to be able to hit this switch, then the real fix would be to replace the `llvm_unreachable` with an `Error` or some sort of debug printing etc.

That's a good point, thanks @jh7370! I think at this moment, all cases are handled but if we ever plan to extend it, the `llvm_unreachable` would be hit so I agree emitting an actual error makes sense. I've removed the unreachable in this PR.

https://github.com/llvm/llvm-project/pull/207118