2. Select "Staging" schema

Staging schemeがリポジトリに入ってないみたい。 https://github.com/kishikawakatsumi/Xcode10-NewBuildSystem-SWIFT_ACTIVE_COMPILATION_CONDITIONS-Bug/tree/master/App.xcodeproj/xcshareddata/xcschemes (edited)

kishikawakatsumi/Xcode10-NewBuildSystem-SWIFT_ACTIVE_COMPILATION_C...

Xcode 10's new build system sets a wrong SWIFT_ACTIVE_COMPILATION_CONDITIONS flag if using xcconfig file. - kishikawakatsumi/Xcode10-NewBuildSystem-SWIFT_ACTIVE_COMPILATION_CONDITIONS-Bug