when one merges a package a copy of the ebuild used is kept but the eclass those ebuild may depend on are not having portage put a copy of these in those directorys might be a good idea Reproducible: Always Steps to Reproduce:
I'm considering taking a copy of the environment file maintained by ebuild.sh and using the exported functions to handle this... Still brewing it over.
Seems that you've done it (environment.bz2)
*** Bug 43009 has been marked as a duplicate of this bug. ***