そのあたり改善するはずのPRが、最初の申請から1年近くに… https://github.com/apple/swift-package-manager/pull/1406

[Xcodeproj] Avoid generating module.modulemap if umbrella header exists, on creating Clang Module targets by norio-nomura · Pull Request #1406 · apple/swift-package-manager

This was rewritten #955 for master. This PR increases the portability of generated Xcode project by reducing the use of module.modulemap which absolute path contains. If clang module has umbrella...