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

[James Henderson via llvm-commits]

jh7370 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.

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