Problem inheriting from image

[pfichtner]

Writing my own Dockerfile inheriting from andrius/asterisk where I add some files to /var/lib/asterisk/sounds/ I run into the problem that in my parent Dockerfile (andrius/asterisk) the directory is defined as VOLUME
Because of that all the files added by my Dockerfile during build process are gone when starting the container (see https://stackoverflow.com/questions/46227454/modifying-volume-data-inherited-from-parent-image and https://docs.docker.com/engine/reference/builder/#notes-about-specifying-volumes).

I could add the files during container startup (via ENTRYPOINT) but that would mean that on each startup the sound files would have to been downloaded.
Currently I use a copy of your Dockerfile without the VOLUME commands.

Both solutions are workaround/hacks. Do you have an idea how to solve this issue in a clean manner?