Provide a helper script/instructions to package up a non-gitian compiled Firefox for Gitian
An easy way to allow incremental developer (re)builds is to provide a helper script that wraps up a non-Gitian compiled Firefox component into a gitian compatible input zip, so you can incrementally rebuild Firefox and only have to wait through a re-bundling step to produce a working Linux bundle that is otherwise as close to an official TBB as possible.
We should also document this process in the Hacking file and/or Gitian README.