[llvm] [ObjCopy] Reject compress-debug-sections for non-ELF (PR #191314)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

> Thanks, basically looks good. I've added @mstorsjo, in case he wants to take a quick look.
> 
> I noticed that in #193965, @mstorsjo used `Common.compressSections` instead of `Common.CompressionType`. Could you take a look and see what the functional difference is between the two, i.e. when are they used/not used and do the two checks have the same overall result?

`Common.compressSections` is used for the `--compress-sections` option (which also is only implemented for ELF), while `Common.CompressionType` is used for `--compress-debug-sections`.

https://github.com/llvm/llvm-project/pull/191314