Xcode compilation cache now works with SwiftPM dependencies that use module maps

Generated projects that include SwiftPM packages carrying custom module maps (for example, Objective-C packages or swift-atomics shims) previously failed to build when Xcode compilation caching was enabled, showing a permission error from the Copy Module Map script phase. The generated phase now copies module maps with cp -f, which overwrites the read-only outputs produced by the cache. Cached builds now succeed for those projects.