Cache static Objective-C xcframeworks with nested module headers behind dynamic deps

Static Objective-C xcframeworks whose headers live under Headers/<ModuleName>/ and cross-import each other via the framework-prefixed form (like ARCore’s ARCoreGARSession and ARCoreGeospatial) are now consumed through the xcframework’s own module.modulemap with the Headers root on the search path. The flat layout path is unchanged, so cached ARCore-targeting tool targets build cleanly when they are routed through the binary cache.