The main thing from a project maintenance perspective is for platforms to
not become a burden to other code maintainers. PRs need to be reviewed. Every #if/#endif in code is a cognitive burden. So being a minor platform can come with unexpected breakages that need fixing due to other changes made in the codebase that did not pay attention to the platform. As we cannot expect everyone working on code to care about anything beyond the tier-1 fully supported platforms, buildbot or not.
Yes, but all this doesn't apply here. We're literally talking about a few lines of autoconf and preprocessor defines . In fact, the change to remove "s390 support" (in quotes because these few lines don't really can be considered platform-specific code), introduces more lines than it removes because of the comments.