Electron addons] Handle building for multiple architectures

Today when the app builds, we build for the arch of the current machine.

This is a good default. But if I'm on x64, I want to be able to build an arm64 package. How can I do this?

We'll need a solution that works nicely with electron forge, and make sure the create-addon command does the right thing.

Start by reviewing the Electron Forge integration and the create-addon command entry point. Define how a build on one architecture should target x64 or arm64, then verify that the addon package is produced correctly for each supported architecture.

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