swift

f175e66a - [Driver / API Notes] Re-introduce "-apinotes" driver flag to compile API notes.

[Driver / API Notes] Re-introduce "-apinotes" driver flag to compile API notes. Using Clang to compile API notes introduces a dependency on the underlying Clang, which can cause problems as Clang's support for API notes evolves. Re-introduce the "-apinotes" driver flag into the Swift driver to allow us to compile API notes, and use that (rather than Clang) to precompile API notes for the overlays.