Downloading and caching globally

[jodersky]

I'm looking into downloading a static binary as part of a mill task. This binary will be used over and over again, and I'd like to cache the file machine-wide (basically share it even across completely different mill projects).

Is there already something in mill which provides this out of the box? I could probably do this manually and just dump the file to a hard-coded location such as ~/.cache/???, but a built-in feature would be more convenient.

[alexarchambault]

#4066 shows how to use coursier for that. For a broader discussion about that problem, see #3930 though.