Overriding Xcode's llbuild with a custom llbuild binary

[chiragramani]

A custom Swift driver toolchain can be used in Xcode by overriding the SWIFT_EXEC as documented in the swift-driver README (https://github.com/apple/swift-driver).

As we are experimenting with llbuild changes locally, how can we point Xcode to use the custom llbuild - mostly for checking the impact of the changes on the end-to-end developer workflows in a production Xcode environment?

[shepting]

We would love this as well.