Fix Swift-only package framework modulemaps in Tuist cache

Resolves a build failure when using tuist cache with SwiftPM products that are promoted to frameworks. Swift-only framework targets previously lacked a Tuist-provided modulemap, so Xcode synthesized one that referenced the Swift compatibility header before it was emitted. Tuist now generates a minimal modulemap for these targets and disables Xcode’s synthesized modulemap, preventing the header-not-found error and keeping caching reliable for these dependencies.