build : fix build for Xcode versions older than 13.x
UIKeyCommand.wantsPriorityOverSystemBehavior
is introduced in iOS 15 SDK but we actually still use Xcode 12.4 on CI.
This old Xcode version only provides SDK for iOS 14.4 max, making this api unavailable to compiler.
Hence we use ObjC apis to call the method and still have the ability to build with older Xcode versions.
Should fix build for videolan/vlc-ios!527 (merged)
Edited by Maxime Chapelet