strip-nondeterminism "is a Perl module for stripping bits of non-deterministic information, such as timestamps and file system order, from files such as gzipped files, ZIP archives, and Jar files. It can be used as a post-processing step to make a build reproducible, when the build process itself cannot be made deterministic. It is used as part of the Reproducible Builds project."

Browse source @ https://anonscm.debian.org/cgit/reproducible/strip-nondeterm...

PS. non-deterministic filesystem order .. doesn't this go away if you use tmpfs?