mac/compat: add withLock fallback for xcode older than 14

withLock is available for macOS versions starting from 10.10 but can
only be used on xcode 14+. xcode 14 introduced swift 5.7, so we guard it
behind a swift version check.

osdep/mac/swift_compat.swift

@@ -15,6 +15,16 @@
  * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#if !swift(>=5.7)
+extension NSCondition {
+    func withLock<R>(_ body: () throws -> R) rethrows -> R {
+        self.lock()
+        defer { self.unlock() }
+        return try body()
+    }
+}
+#endif
+
 #if !swift(>=5.0)
 extension Data {
     mutating func withUnsafeMutableBytes<Type>(_ body: (UnsafeMutableRawBufferPointer) throws -> Type) rethrows -> Type {