[strmpnk]

Thanks for this tip. I find myself a little more reluctant to rely on environment variables for this sort of thing but it'd be fair to say the same about filesystem state.

My only problem with this solution is that it changes the mix configuration itself (which is version controlled) which is fine if others are in need of similar overrides when working on the project. For one-off/local things, it can be a bit heavy for temporary overrides.

Still, it's a fair trade-off since it's a lot easier to code up logic like this with mix compared to rebar3.