IMO there is absolutely no reason to enable warnings in CI without -Werror. Nobody reads the logs of a successful build.

If some warnings are flaky then disable them specifically. In my experience most warnings in -Wall are OK and you can suppress the rare false positives in code. Don't suppress without a comment.

edit:

Having said that there are entirely valid reasons to not have -Werror outside of CI. It should be absolutely disabled by default if you distribute source.