swift

cb0720b7 - Package CMO: Prevent serializing types from SDK/system modules imported as @_implementationOnly.

Package CMO: Prevent serializing types from SDK/system modules imported as @_implementationOnly. Currently, types from @_implementationOnly modules can be serialized into client modules if their defining modules are SDK or system modules. However, @_implementationOnly is intended to hide types from external clients, and may cause the type’s metadata (e.g., field offsets) to be stripped. If such types are serialized and later accessed by a client module, it can lead to linker errors due to the missing metadata. This PR prevents all types imported with @_implementationOnly from being serialized. Resolves rdar://144181455