`cache: yarn` doesn't work for a self hosted runner

In the documentation, there is a section called Caching packages dependencies, which suggests to use cache: yarn for caching yarn dependencies.

On GitHub runners, it works, since GitHub runners have both node and yarn already installed, and therefore there is no problem. On self-hosted runner, this is not a case.

Which leads us to a catch-22 situation: setup-node action actually expects node to be installed (together with yarn).

Therefore, the action itself fails (since it cannot run yarn during setup).

My proposal is maybe to actually install yarn during the action, at least if we need it for action to success.

Thanks!

[yhaskell]

So, basically the idea is to not use setup node to set up node on the self hosted runners?

[yhaskell]

Basically, I have to install node, to be able to install node. That sounds counterintuitive, and wrong