mac: fix build on older swift versions

this is apparently something that was added with swift 5.5, though it is
hard to find anything officially.

don't capture self in closure but explicitly access all variables by
prepending self.

Fixes #12653

video/out/mac_common.swift

@@ -111,11 +111,11 @@ class MacCommon: Common {
                                          _ flagsOut: UnsafeMutablePointer<CVOptionFlags>) -> CVReturn
     {
         let frameTimer = mpv?.macOpts.macos_render_timer ?? Int32(RENDER_TIMER_CALLBACK)
-        let signalSwap = { [self] in
-            swapLock.lock()
-            swapTime += 1
-            swapLock.signal()
-            swapLock.unlock()
+        let signalSwap = {
+            self.swapLock.lock()
+            self.swapTime += 1
+            self.swapLock.signal()
+            self.swapLock.unlock()
         }
 
         if frameTimer != RENDER_TIMER_SYSTEM {