[llvm] [llvm-objdump] Support --mcpu=help/--mattr=help without -d (PR #165661)

[Ruoyu Qiu via llvm-commits]

cabbaken wrote:

I prefer to add archive support as part of this PR later. This won't be a heavy workload, I believe.

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