Support for Mac Catalyst

[robertying]

Bug Description

React Native 0.64-rc has introduced Hermes for iOS. I'm trying to build for Mac Catalyst and there seems to be some problem with prebuilt binary shipped with Hermes for iOS.

ld: building for Mac Catalyst, but linking in dylib built for iOS Simulator, file '/Users/rying/myapp/ios/Pods/hermes-engine/destroot/Library/Frameworks/iphoneos/hermes.framework/hermes' for architecture x86_64

- [ ] I have run gradle clean and confirmed this bug does not occur with JSC

Hermes version: 0.7.2
React Native version (if any): 0.64.0-rc.3
OS version (if any): macOS 11.2.1
Platform (most likely one of arm64-v8a, armeabi-v7a, x86, x86_64): x86_64 (Catalyst)

Steps To Reproduce

1. Init RN with 0.64.0-rc.3
2. Build for Mac Catalyst target

The Expected Behavior

I see Hermes already supports x86-64 so it should play nice with Catalyst too.

Thanks for the great work and I really hope it gets fixed soon!

[Huxpro]

@robertying Hey thanks for reporting this interesting use case!

Just let you know that the community is currently prioritizing shipping the stable 0.64 first. Once the release is out there will be more community resources to investigate additional features/bugs. cc @grabbou

[Arkkeeper]

This issue seems to be related with mine #468

Hermes as a framework is compiled for certain architectures and platforms (iOS, iOS Simulator or macOS), and then they are merged into a fat framework with lipo.

For a proper compatibility with Mac Catalyst (and arm64 iOS Simulators on M1 Macs) Hermes should be compiled as .xcframework containing slices for all necessary archs and platforms. For example, OpenSSL.xcframework shipped along with Flipper, has 4 slices:

I've forked Hermes and managed to add arm64 iOS Simulator support. Unfortunately, I haven't figured yet how we should pass necessary cmake flags for building Catalyst version.

Our team has been using React Native app with Catalyst in production for more than a year, and Hermes support would be great.

[Huxpro]

This is fixed by #546 (was #543 and #475) and would be available when Hermes 0.8.1 is out (together with RN 0.65 stable).

Thanks everyone involving!