fix(package): set process.env.npm_config_arch for each arch in universal build

[busterbogheart]

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Summarize your changes:

Closes #3657

This one line will set process.env.npm_config_arch to the appropriate architecture as the build creates multiple versions for the Mac universal app.

[erickzhao]

Hey @busterbogheart,

Thanks for the PR on this and sorry for the lack of response on the original issue.

This seems reasonable to me, but I pushed up a new commit to be more intentional about setting this env var specifically for packaging universal apps: c012573

Can you let me know if this works for you?

[MarshallOfSound]

Hey @busterbogheart can you provide a sample basic electron app that has the problem you're describing that is fixed by the fix you're proposing.

Not entirely sure how this fixes things, and having that repro would potentially allow us to find a more safe solution.