[llvm] [llvm-objcopy] Report unsupported formats before compression (PR #202357)

[James Henderson via llvm-commits]

https://github.com/jh7370 commented:

Please try to avoid force pushes, as the change in commit hashes trashes the review experience (note that I cannot filter to "changes since last review" as a result). If rebasing is needed, the better approach is to use a merge commit from main, since all commits get squashed and the merge will disappear when the PR lands (we use "Squash & Merge" in LLVM).

The PR description becomes the final commit message that lands in main. As a result, I have a few comments about that:
- Please remove the line saying you didn't use AI assistance. It was useful for me to see that, but it doesn't need to be in the final commit message. For the record, if you post further PRs in the future, I'd put any similar comments (i.e. ones that are for reviewer attention that aren't relevant to the final commit message) in a separate comment posted immediately after you create the PR.
- You need to reword your description to better match what the final behaviour of the PR is.
- It would be worth a note explaining why you've added the zlib requirement to the compress-sections-within-segment test.

Finally, given the slight change in behaviour, it would probably be worth adding a note in the release notes about reporting missing zlib/zstd in cases where the code didn't before, so that people with bad command-lines don't suddenly end up with failing builds that weren't failing before.

https://github.com/llvm/llvm-project/pull/202357