Allows us to switch out debian files and rpm specs on the fly and also gives us an out to have ARCH specific dockerfiles if we need them for RPM's. The same strategy can be used for DEB's if need be Signed-off-by: Eli Uriegas <eli.uriegas@docker.com> Upstream-commit: b72dc2edb8329151bfe2df6989fb329f41e720fb Component: packaging