Run CI on Xcode 13 / Swift 5.5

[johnfairh]

Something odd going on with line numbers coming out of SourceKit but the result is better 🤷🏻 .

Realm ObjC changes because the importer is generating async Swift functions for me -- I have macOS 12 locally so expect (hope) CI on macOS 11 will fail. GitHub Actions doesn't seem to know anything about macOS 12....

Something odd going on with xcodebuild meaning I need to explicitly set a destination to avoid a spammy warning.

Swift 5.5 has changed how typealiass are treated in interface generation to "look through" the typealias more often, meaning the declaration comes out differently to what the user has written. Affects Realm Swift. Will pursue upstream; affects DocC etc. too.

[johnfairh]

Baffled by this:

CI is on macOS 11, Xcode 13.0 has only a macOS 11.3 SDK .. so I suppose somehow it's defaulting min-deployment-target of macOS 12?

SR-15202 for the typealias printing bug - I'm pretty sure it is a bug, it only happens in generic constraints.

[johnfairh]

For my reference: generating the module interface for ObjC like this generates both Swift APIs, one with async and one traditional. When we xref the ObjC method's USR though we get the async one back -- the find-usr API only returns one value. Need to check whether these two decls really share the same USR, if there's anything sourcekitten can do to retrieve them both...