swift

f6a4d426 - [ClangImporter] Update AvailAttr import for "macosx" to "macos" rename. (#3476)

[ClangImporter] Update AvailAttr import for "macosx" to "macos" rename. (#3476) This resolves a number of failing tests caused by availability attributes not getting imported for macOS. (cherry picked from commit 4b566df9f3eeb8a5255afcd265722dd9e8fc37d0)