The issue IMO isn't -Werror, it's -Wall, -Wextra, and -Weverything. If you individually specify the warnings you want, other compiler versions won't have a diff

The issue IMO isn't -Werror, it's -Wall, -Wextra, and -Weverything. If you individually specify the warnings you want, other compiler versions won't have a different list. So -Werror won't cause your build to fail because some other compiler (or version) had a different -Wall list.