How to create a fat binary on xcode 10

Question

I am trying to make a fat binary of my library using XCode 10 (10A255) Using Fastlane:

xcodebuild(
        workspace: "Mylibrary.xcworkspace",
        scheme: "Mylibrary",
        configuration: "Release",
        clean: true,
        archive: true
    )

But running lipo -i ~/Mylibrary.framework/Mylibrary I only get armv7 arm64 that does not run on simulators.

Does anyone know the reason why this happens?

PS: The same command is working on Xcode 9.4 and lipo -i prints i386 x86_64 armv7 arm64 which works fine.

Mccartan