[llvm] [LLVM][MC] Add tracing support to llvm-mc to profile decoding (PR #151149)

[Fangrui Song via llvm-commits]

MaskRay wrote:

Perhaps shorten the option to `--runs`? (At least, I don't think the infix `-benchmark` is useful..)

Since this doesn't really touch lib/MC include/llvm/MC, I'd remove the `[MC]` tags. perhaps: `[llvm-mc] Add --runs for benchmark`

https://github.com/llvm/llvm-project/pull/151149