if it is possible to take advantage of mdbook-linkcheck caching now?

Azure has a beta preview of caching, but the rust repo does not use it. Typically s3 buckets are used, but I do not know anything about them or whether it would be appropriate to use.

Originally posted by @ehuss in #66338 (comment)

Splitting this off from the other thread so as not to clutter it.

@pietroalbini Is something like the above possible? Basically, we just want to cache the src/doc/rustc-guide/book/linkcheck directory between builds. This directory is generated by the linkchecker. Doing this would significantly reduce timeouts and other networking issues when linkchecking... We already use this functionality on the rustc-guide repo with Travis caching...