to make Auv3 works (using juce cmake but not the add plugin part), I had to
set_target_properties(${TARGET_EXT_NAME} PROPERTIES
BUNDLE YES
BUNDLE_EXTENSION appex
XCODE_ATTRIBUTE_WRAPPER_EXTENSION appex
XCODE_PRODUCT_TYPE com.apple.product-type.app-extension
XCODE_ATTRIBUTE_APPLICATION_EXTENSION_API_ONLY NO
)
and copy into SA bundle
add_custom_command(TARGET ${TARGET_SA_NAME} POST_BUILD COMMAND ${CMAKE_COMMAND} ARGS -E copy_directory “$<TARGET_FILE_DIR:${TARGET_SA_NAME}>/…/${TARGET_EXT_NAME}.appex” “$<TARGET_FILE_DIR:${TARGET_SA_NAME}>/PlugIns/${TARGET_EXT_NAME}.appex” MAIN_DEPENDENCY “${TARGET_EXT_NAME}”)