I am trying to run the test target of a Swift package in Xcode in release mode without generating an Xcode project.
However, when I set the build configuration of the test scheme to release, the build fails because of a missing -enable-testing flag that has to be passed to the compiler when @testable import is used.
How can I add this flag in Xcode for a Swift Package? Note that the traditional build configuration options are not available because no Xcode project exists. Adding -Xswiftc -enable-testing as launch arguments for the test scheme does not work.