[PATCH 0/3]; ruby-build-system improvements.

[Ben Woodcroft]

Hi all,

Attached is a patch to make the building gems with native extensions
reproducible, and a another to introduce a phase to remove `git ls-files` in
Rakefiles as suggested by Dave:
http://lists.gnu.org/archive/html/guix-devel/2016-06/msg00262.html

With these patches and some other small fixes not mentioned most/all of the
Ruby packages build reproducibly.

Thanks as usual for any review.
ben