How to handle CI build coverage uploads?

[rollbear]

The state of things right now is that (line) coverage is collected with kcov for Linux builds only, and is forwarded to codecov.io.

There are several problems here, however.

• kcov is (not quite, but effectively) linux only, and it is incompatible with sanitizer builds, which requires a separate step. This project is not married to kcov, so we can use other solutions.
• codecov.io has a limit on the number of coverage uploads it accepts for a single commit SHA-1. We're currently close enough to that limit that a release-push to main plus a tag for the same commit causes uploads to fail because the number of allowed uploads for one commit has been exceeded.
• Regardless of why, the failure to upload coverage information is not a cause to fail a build, even though it is worthy of notice. Is there a middle ground between pass/fail? I have no problem with a release tag build failing an upload if it refers to a successful build of the same git commit, but i also want successful coverage information to PR builds so that I can easily judge if the PR should have more tests or not.
• Can we improve this by collecting coverage information for non-linux builds?

What options do we have to improve the above? Discus