Don't build SDL_JOYSTICK_HIDAPI by default on iOS

If you enable this, you'll need to link with CoreBluetooth.framework and add something like this to your Info.plist:
<key>NSBluetoothPeripheralUsageDescription</key>
<string>MyApp would like to remain connected to nearby bluetooth Game Controllers and Game Pads even when you're not using the app.</string>

src/hidapi/mac/hid.c

@@ -19,6 +19,9 @@
  code repository located at:
  http://github.com/signal11/hidapi .
  ********************************************************/
+#include "../../SDL_internal.h"
+
+#ifdef SDL_JOYSTICK_HIDAPI
 
 /* See Apple Technical Note TN2187 for details on IOHidManager. */
 
@@ -1184,3 +1187,5 @@ int main(void)
 	return 0;
 }
 #endif
+
+#endif /* SDL_JOYSTICK_HIDAPI */