あまりよくわかっていないのだけど、たぶんクロスコンパイル用のtoolchainを用意しなければいけないのと同じなんだと思ってる。 https://github.com/apple/swift-package-manager/pull/1098

cross compilation support (configurable destinations) by weissi · Pull Request #1098 · apple/swift-package-manager

General This adds experimental support for cross compilation or more precisely configurable destinations for binaries to SwiftPM. The basic idea is that you hand a JSON file in the format described...