swift

2d86330c - Always add an implicit import of 'Cxx' module when C++ Interop is enabled.

Always add an implicit import of 'Cxx' module when C++ Interop is enabled. We cannot always rely on being able to do so only as an overlay query upon loading 'requires cplusplus' modulemap modules. The 'requires' statement only applies to submodules, and we may not be able to query language feature modulemap attributes in dependency scanning context.