REF: workaround docker without buildkit's lack of COPY --chmod support

Author: westurner

repo2docker/buildpacks/base.py

@@ -186,8 +186,11 @@
 
 # Add entrypoint
 ENV PYTHONUNBUFFERED=1
-COPY --chmod=0755 /python3-login /usr/local/bin/python3-login
-COPY --chmod=0755 /repo2docker-entrypoint /usr/local/bin/repo2docker-entrypoint
+COPY /python3-login /usr/local/bin/python3-login
+COPY /repo2docker-entrypoint /usr/local/bin/repo2docker-entrypoint
+USER root
+RUN chmod 0755 /usr/local/bin/python3-login /usr/local/bin/repo2docker-entrypoint
+USER ${NB_USER}
 ENTRYPOINT ["/usr/local/bin/repo2docker-entrypoint"]
 
 # Specify the default command to run