"Quick checks" despite the name take 7-10 minutes

[ulysses4ever]

Originally posted by @geekosaur in #10421 (comment)

A quick look at the Doctest and buildinfo filed generator jobs (e.g. this and this) shows that they seem to do repetitive builds: they first build a thing and then run it but the running also does the building again first. For Doctest, it looks like magic and we should ask the author. For the generator, it seems like a blunder on our side.

Besides, setting up a GHC via GHCup takes 2 minutes. There's probably nothing we can do about that.

[ulysses4ever]

I guess Doctest isn't bad because the initial build is only ~28 seconds.