Ok. Yes, I see you copy over the entrypoint.sh file from the previous stage. So you do have it there. 
When I’m trying to debug a Dockerfile, I find it helpful to build it locally and get a CLI into it to see if things are where I expect them to be, etc.
docker run -it --rm my_app /bin/ash
This starts the container using ash instead of bash as the shell, since that’s what Alpine Linux uses by default.
Otherwise I don’t know what problem you are hitting.