swift234

[CMake] Stop using globs on the apinotes directory.

The problem here is that there isn't an obvious way to force a CMake
reconfiguration when you need to add new apinotes. This dates back to
when we (internally) had the apinotes in a separate repo, but that
hasn't been the case for a long time.

We're still not using a /normal/ CMake add_subdirectory for these
because we compile the apinotes as part of building overlays for
frameworks that have both overlays and apinotes, and I didn't want to
touch any of that stuff right now.