link a source of docker volumes comment

library_generation/postprocess_library.sh

@@ -76,6 +76,7 @@ preprocessed_libraries_binding="${owlbot_cli_source_folder}"
 # being mapped from the host machine to the child container (instead of the
 # parent container to child container) because we bind the `docker.sock` socket
 # to the parent container (i.e. docker calls use the host's filesystem context)
+# see https://serverfault.com/a/819371
 # We solve this by referencing environment variables that will be
 # set to produce the correct volume mapping.
 #