Nested static-objc xcframeworks like ARCore build through the binary cache

ARCore and similar Google SDK xcframeworks can now be cached and consumed through the binary cache. Static Objective-C xcframeworks with nested, prefix-self-importing headers (for example ARCoreGARSession / ARCoreGeospatial) are now consumed via the xcframework’s own module map and Headers root in one defined place, so <ModuleName/Sibling.h> imports resolve and the module is no longer defined twice. Earlier fixes that only added the Headers root without the per-layout handling produced either 'ARCoreGARSession/GARTrackingState.h' file not found or import of shadowed module 'GARAnchor' failures.