[Feature] Add support for Mac Catalyst

[willowsokora]

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What did you do?

I compiled an application with mac catalyst enabled

What did you expect to happen?

I expect my application to build

What happened instead?

When compiling the app for iOS, it works fine, but when I compile for mac (or archive) I get a swift compiler error "No such module 'Down'". I have it installed manually, in Xcode 11.3

[iwasrobbed]

Hi @jacobsokora 👋

I always welcome pull requests for new features / compatibilities. I won't be using Catalyst myself anytime soon so I'm leaving this up to the community (you + others) to add support for if needed

[kengruven]

FWIW, I just ran across Carthage/Carthage#2799 -- It looks like Carthage doesn't yet support Catalyst. That's probably the biggest blocker for Down (at least for Carthage users), since Down.framework already builds on macOS and iOS.

[iwasrobbed-ks]

I just tried this on a Mac Catalyst app and it works fine. Seems more like the Carthage issue that @kengruven described (or something else other than just purely Catalyst)

[iwasrobbed-ks]

Feel free to reopen if you have a reproducible project, but working for me as of Xcode 12