cmdstan fails on in actions macOS

[sbfnk]

The install cmdstan action requires a manual clearing of the cache every time to work on macOS - to fix this we could

• revert to manual install
• fix the option upstream (I don't know how)
• something else?

[sbfnk]

And all the actions run fine - will close this for now but can reopen if it reappears.

[seabbs]

I think the thing that is needed is to put a timer on the cache in the action. I don't see a way of doing that from a naive first pass but it seems like an obvious feature it should have