swift

aa2bf6bd - [6.0][Runtime] Don't emit signposts until the system is ready.

[6.0][Runtime] Don't emit signposts until the system is ready. Emitting a signpost for the first time can trigger lazy setup of the logging system, and doing this in the wrong context can cause deadlocks. Check to see if the logging system is already set up, and only emit signposts if it has been to avoid triggering this. As it's hard to determine if the "is it set up?" function is available in the SDK we're building against, only do this in OS builds, as it's not particularly useful in local builds. rdar://124620772 (cherry picked from commit dd24d8e71fe9ca5d625a386cbaa6d67285414867)