[asheldon]

The ability to depend on library versions that do not exist is a misfeature. It should not be possible for someone to build a new version of their software and cause your software to cease building or running.

This doesn't just result in non-reproducible builds, but it results in them at unpredictable times and, if you have servicing branches of your code, backward through time. This is not a good property if you need to know what you are building today is the same as what you built yesterday, modulo intentional changes, or even that it will build or run.