Setting launch image when using CUSTOM_XCASSETS_FOLDER

When using CMake to build there is the option to use a custom xcassets folder by setting CUSTOM_XCASSETS_FOLDER. This implicitly sets a launch image. However with iOS 13 LaunchImages are deprecated. My proposition is to check for the deployment target and only set the attribute if the target is less then iOS 13. See attached patch:

index 245fe233e..dc506e1d9 100644
--- a/extras/Build/CMake/JUCEUtils.cmake
+++ b/extras/Build/CMake/JUCEUtils.cmake
@@ -588,7 +588,7 @@ function(_juce_generate_icon source_target dest_target)
 
         get_target_property(add_storyboard ${source_target} JUCE_SHOULD_ADD_STORYBOARD)
 
-        if(NOT add_storyboard)
+        if(NOT add_storyboard AND CMAKE_OSX_DEPLOYMENT_TARGET LESS 13)
             set_target_properties(${dest_target} PROPERTIES
                 XCODE_ATTRIBUTE_ASSETCATALOG_COMPILER_LAUNCHIMAGE_NAME "LaunchImage")