Introduce EMBROIDER_WORKING_DIRECTORY env var for concurrent builds

[simonihmig]

Backporting #2270 to stable.

[simonihmig]

Failing tests seem to be a general issue on stable!?

[mansona]

@simonihmig yes that's true, since Ember 6.1 we can't rely on the auditing system because we now rely on exports in package.json 😞 We discussed this with @ef4 and we have a very soft "let's not change stable" since we're so close to getting the new release out, the reason being that it would be a significant effort to fix the audit system on stable

I don't know how we want to proceed on this 😞

[simonihmig]

For my understanding, what is the "auditing system"? 😅

So after having migrated hundreds of addons to v2 and Embroider compatibility, we are only now in the process to migrate production apps to "stable" Embroider + webpack. It might take us quite a while to be able to adopt Embroider/Vite (for existing apps), pending Ember upgrades but also some other roadblocks potentially (left over AMD shenanigans).

So I do expect us to be on Embroider/webpack for a while. I don't expect new development there of course, but I/we would appreciate if we could still have it in some kind of maintenance mode, to accept an occasional bug fix or land some low hanging fruits like this one.

I don't know how we want to proceed on this

If it is only for Ember 6.1+, can we limit the test matrix to only run on earlier versions?

[ef4]

I don't think it's only a bug in the audit system. On stable, nodeResolve is used for more than just audits. It's used for resolving components for example. It's only on main where we've been able to unify all resolving through the prevailing environment.