investigate: CI is not building properly?

[colemickens]

A few weeks ago I noticed that the update script is either not building, or not properly failing on failed builds.

I think this was also observed by @Artturin, seeing a failure exposes in a published rev.

I should have filed this a while back. I don't know if I can look into this soon. The main update script probably deserves a pass through. It would also maybe be a good time to experiment and see if nix-update is smart enough, or can be told appropriately which file to write the update-diffs to.

[colemickens]

I'm going to remove the isCached stuff, and then give it a bit and see how things go.

But also, there's a build failure on master again, so something is likely still weird somewhere.