propose a different caching strategy in sccache-action

[sylvestre]

Currently, sccache-action uses the strategy described here: https://github.com/mozilla/sccache/blob/main/docs/Architecture.md the storage being GitHub action storage. it is storing a artifact per file.

It causes some issues like:

• rate limiting (we have often artifact not stored because GHA is rejecting them)
• we store a lot of things

We should consider having a new configuration parameter to use a local copy of the cache instead.

The process would be:

1. if it exists, download the cache storage (file single) and unpack it
2. set up sccache to use the local unpacked cache directory - with direct access (by default in 0.7.2)
3. after the build, upload the new local cache directory in the github storage

If there is no cache available, skip step 2, just start sccache as local

[russkel]

I run sscache from within Docker on Actions so this would be a good idea.