CI: Improve Windows dependency caching

[hoffie]

What is the current behaviour and why should it be changed?

Some of the Windows dependency downloads (I'm suspecting SourceForge) increasingly fail.

Get-RedirectedUrl : Exception calling "GetResponse" with "0" argument(s): "The request was aborted: Could not create 
SSL/TLS secure channel."

https://github.com/jamulussoftware/jamulus/runs/7742832728?check_suite_focus=true#step:9:1

Describe possible approaches ~~More~~ Proper binary caching would reduce the impact.

Has this feature been discussed and generally agreed?

The increased build failures have been discussed via chat recently.