Building container application

I'm building the application containers for the Hello World example following the RoboMaker Developer Guide. I have downloaded it from git, added under the helloworld folder the Dockerfile and the entrypoint.sh by coping and pasting them from the guide.

My question is: how do I have to change the entrypoint.sh file? Because the guide says "You may want to add your own environment configuration steps to this ENTRYPOINT file" ,

If I build the robot application using this command: "DOCKER_BUILDKIT=1 docker build . --build-arg ROS_DISTRO=melodic --build-arg LOCAL_WS_DIR=./robot_ws --build-arg APP_NAME=helloworld-robot-app -t robomaker-helloworld-robot-app" the following error pops up: "failed to solve with frontend dockerfile.v0: failed to read dockerfile: open /var/lib/docker/tmp/buildkit-mount171637073/Dockerfile: no such file or directory"

If it helps, the setup.bash and setup.sh files are both under helloworld/robot_ws/install and helloworld/simulation_ws/install folder, while the code for entrypoint.sh is as follows:

#!/bin/bash

set -e

source "/home/$USERNAME/workspace/$APP_NAME/setup.bash"

if [[ -f "/usr/share/$GAZEBO_VERSION/setup.sh" ]]

then

source /usr/share/$GAZEBO_VERSION/setup.sh

fi

printenv

exec "${@:1}"