swift

288f37b2 - [Concurrency] [shims] Don't declare `exit` in the concurrency shims

[Concurrency] [shims] Don't declare `exit` in the concurrency shims Don't delete the OS declaration of `exit` because the concurrency shims aren't always imported, and so the shim declaration might not always be available. Don't override the OS declaration of `exit` in the concurrency shims since we can't just delete the OS one. Instead, set up internal shims just for building Concurrency that forward declares `exit`.