[llvm] [objcopy] Add aliases to some llvm-objcopy --subsystem options (PR #98036)

[James Henderson via llvm-commits]

https://github.com/jh7370 approved this pull request.

Thanks, LGTM, with some suggestions for the commit title.

I suggest adding the `[COFF]` tag to the PR title before landing. Also, the tag should be `[llvm-objcopy]`, since simply `objcopy` tends to refer to the GNU tool. Finally, to shorten the title, you can drop the "llvm-objcopy" bit after "some", since it is made redundant by the tags:
```
[llvm-objcopy][COFF] Add aliases for some --subsystem options
```

https://github.com/llvm/llvm-project/pull/98036