It seems like BuildKit is the next generation, but not likely to be
enabled by default soon (https://github.com/moby/moby/issues/40379).
Add a flag so people who want to use its features can easily opt-in.
Change-Id: I862819959c77a557199f64b4d42109bc7915959c
In certain build projects, multiple Dockerfiles exist (for example,
one per distro) to simplify reading. However, this role is hardwired
to use dockerfiles only named "Dockerfile".
This is a problem, as you can't override the filename neither per
image, or globally.
This should fix the problem, allowing certain images to be build
by providing the dockerfile argument in docker_images, but also
have a globally overridable flag if you are using a different
convention (for example Dockerfile.distro_minordistroversion).
Change-Id: I075c365bc9f4f85f9ada832d22d1f1e213e68e21
Ian Wienand