Cached xcframework module map dependencies build reliably

Targets that depend on precompiled xcframeworks with module maps (including Google SDKs like ARCore, Firebase’s nested static Objective-C libraries, and others) can now be consumed through the binary cache without redefinition errors, missing prefixed imports, or shadowed module errors. The mapper distinguishes nested header layouts from flat ones, points -fmodule-map-file at the xcframework’s own module map where appropriate, and skips adding redundant headers when Xcode already extracts the module map via ProcessXCFramework.