The concurrency runtime now deploys back to macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, which corresponds to the 5.1 release of the stdlib.
Adjust macro usages accordingly.
Rather than blanket-disabling concurrency tests when we aren't using a
just-built concurrency library, enable them whenever we have a
suitable concurrency runtime, either just-built, in the OS, or via the
back-deployment libraries.
introduce new options parameter to all task spawning
[Concurrency] ABI for asynclet start to accept options
[Concurrency] fix unittest usages of changed task creation ABI
[Concurrency] introduce constants for parameter indexes in ownership
[Concurrency] fix test/SILOptimizer/closure_lifetime_fixup_concurrency.swift
This allows programs to target older OSes while using Concurrency behind an availability check. When targeting older OSes, the symbols are weak-linked and the compiler will require the use of Concurrency features to be guarded by an availability check.
rdar://75850003