swift

276706ec - Don't abort on Linux if `withLockIfAvailable()` is called recursively. (#85448)

Don't abort on Linux if `withLockIfAvailable()` is called recursively. (#85448) On all platforms except Linux, calling `withLockIfAvailable()` recursively just returns `nil`. However, our Linux implementation chooses to abort the process instead. We don't need this inconsistent/destructive behaviour and can just return `nil` as we do elsewhere.