Reminder: Pull request CI checks will break on May 1

[Ryan Schmidt]

On Apr 23, 2021, at 07:08, Ryan Schmidt wrote:

> The Bintray service will cease to exist on May 1. Our pull request CI checks rely on being able to download certain assets from Bintray, so unless we do something to fix this before then, our pull request CI checks will no longer work as of May 1.
> 
> https://jfrog.com/blog/into-the-sunset-bintray-jcenter-gocenter-and-chartcenter/

I've moved the files to https://distfiles.macports.org/_ci/ and updated the CI bootstrap scripts accordingly. This is not necessarily their final home, and does not yet accommodate the automatic updating we had before, but is just intended to prevent things from breaking on May 1 and give us time to think about what the best solution is.

Any old pull requests that haven't been merged yet that still reference the BinTray files will still fail to build after May 1. The solution would be to rebase those PRs against master and force push.