Build can’t install Ruby after upgrade to new image

[hrishikesh]

If you wish to know, there’s a detailed explanation behind this here:

Build fails with Focal image due to unwanted old Ruby

To give a little context, the practice of pinning dependency versions was started in the early days of Netlify, with the goal of making sites “just work” out f the box, and continue working even if default versions on the build image change. The pinning happens for Ruby, Node, Yarn, and Go, and happens for all sites, because it’s difficult to clearly identify that a site isn’t using a language. However, as we started introducing new build image versions, and now are deprecating old ones, this p…