Xcode 12ではiOSデバイス向けとApple Silicon Macで動くiPhone Simulator向けのどちらにもarm64が含まれるから、carthageがlipoでフレームワークを結合する時エラーになるのね。 https://github.com/Carthage/Carthage/issues/3019

Carthage builds fail at xcrun lipo on Xcode 12 beta (3,4,5...) · Is...

carthage install method: [ ] .pkg, [x] homebrew, [x] source which carthage: /usr/local/bin/carthage carthage version: 0.35.0 xcodebuild -version: 12A8169g Are you using --no-build? No Are you using...