Wire together Swift modules at compile time using the `.swiftmodule` files rather than using the directories containing such files. - The module file is exposed as the artifact shared between projects, rather than its parent directory. - `SwiftBinary.compileImportPath` is replaced with `compileModules`. - `SwiftComile.includes` is replaced with `modules`. - Swift source is now correctly recompiled when an upstream module's API changes, as the module files are now treated as inputs to compilation. Previously they were not.