Bug 1240239 will break a build if someone attempts to build based on an out-dated processed.jar file, because it required changing some paths to be relative to the distdir instead of the bindir. This is also a (less severe) issue for instances where we extend the scope of what ends up in the processed.jar -- the new functionality will not be available until a new processed.jar is generated. A solution for these cases would be to re-generate the jar files if they're older than python/mozbuild/mozbuild/artifacts.py.