I’m new to Docker and want to build a Dockerfile with the following snippet:

RUN 
  cur=`pwd` && 
  wget http://www.coppeliarobotics.com/files/CoppeliaSim_Edu_V4_1_0_Ubuntu20_04.tar.xz && 
  tar -xf CoppeliaSim_Edu_V4_1_0_Ubuntu20_04.tar.xz && 
  export COPPELIASIM_ROOT="$cur/CoppeliaSim_Edu_V4_1_0_Ubuntu20_04" && 
  export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$COPPELIASIM_ROOT:$COPPELIASIM_ROOT/platforms && 
  export QT_QPA_PLATFORM_PLUGIN_PATH=$COPPELIASIM_ROOT && 
  git clone https://github.com/stepjam/PyRep.git && 
  cd PyRep && 
  pip3 install -r requirements.txt && 
  pip3 install setuptools && 
  pip3 install .

Because of the network issue, the build process is unstable and interrupted on the git clone... line. However, when I try to build again, CoppeliaSim_Edu_V4_1_0_Ubuntu20_04 which has already been saved is downloaded again, which consumes a lot of time. Is there any method to skip the download process if the .tar file has already been saved?