CI nightlies

Stream: general

[Johan Commelin]

Now that we have the new CI, how hard would it be to publish oleans for master? Sometimes I work on a PR, and instead of merging lean-3.5.1 into the branch, I merge master into the branch. And then all of a sudden, I need to recompile a whole bunch of stuff, because a can't pull binaries from github.

I wouldn't mind if we only store one set of binaries per day + master. So we could throw away the binaries from old master as soon as a new commit arrives. Does that make sense?