Cache key per executor

I thought I could do this with environment variables but now learn those aren’t available in the cache key naming (brings up another issue of I get no-value for even variables set globally in the project so I don’t know how to invalidate a cache now, but that’s a separate issue).

The issue is needing to distinguish the cache between executors. In this case it is my orb for Erlang/rebar3. Depending on the OTP version being used I need to name the cache based on it because beam files between versions don’t necessarily work, for example if a cache is created compiled from OTP 22 it will then break when run with OTP 21.

Since setting an environment variable for the executor isn’t an option, what is?