[llvm] [llvm-objdump] Eliminate the dependency of `--mcpu=help` and `--mattr=help` on `-d` (PR #165661)

[James Henderson via llvm-commits]

jh7370 wrote:

> I think the test cases I wrote is like a pile of garbage. I'm optimizing them and will push a commit soon. Should I convert this PR to a draft? Additionally, do you think the PR title is suitable for this PR now?

Up to you whether you convert it to a draft. I won't be reviewing it further until I see more commits. The PR title is mostly fine, but a bit long. How about "[llvm-objdump] Support --mcpu=help/--mattr=help without -d"? The description still needs updating, as that is used as the commit message for the final commit that gets landed.

https://github.com/llvm/llvm-project/pull/165661