Add "Architectures" to "generate-stackbrew-library.sh" output

[tianon]

Closes #68

For repos under https://github.com/docker-library, we generally invoke bashbrew from within generate-stackbrew-library.sh to get the Architectures list of the image we're FROM directly, but I wasn't sure if you wanted to add that additional dependency for running the script here, so I wrote a quick one-liner to do the work as a one-off into files that get checked in (which also makes it easier to munge them if it turns out one of them fails to build or doesn't run properly etc and needs to be excluded).

As always, happy to adjust, rebase, amend, etc. I could also set up Travis to test i386, if that's deemed useful (memcached has an example of that: https://github.com/docker-library/memcached/blob/5a09fc033d8e239ebecf1edb20b7f921d51de591/.travis.yml).

[tianon]

🎉 Want me to make the PR over to https://github.com/docker-library/official-images for you, or would you rather take that yourself?

[md5]

That would be great!

…

On Mon, May 21, 2018, 16:23 Tianon Gravi ***@***.***> wrote: 🎉 Want me to make the PR over to https://github.com/docker-library/official-images for you, or would you rather take that yourself? — You are receiving this because you modified the open/close state. Reply to this email directly, view it on GitHub <#89 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAEqT1d0OQIP8OwK2QX5mQM7CqLJTLOXks5t00xtgaJpZM4UHqQ5> .