In terms of user-configurable build flags, they stay the same. Only thing that changes is -o ... parameter, which includes an env: name, but scons uses a full cmdline as a hash for cache storage.
gh action log url
Flow is set run the env, move cache dir, run a different env and then compare both directories
Caches for env:one and env:two are completely different.
Cache for env:one ran the second time is a bit different, but mostly the same (framework.a file has a different timestamps inside)