contrib: move context to repository root, use additional context for copy

contrib/containers/guix/Dockerfile

@@ -74,10 +74,10 @@ RUN usermod -aG sudo ${USERNAME} && \
     echo '%sudo ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
 
 # Copy required files to container
-COPY ./motd.txt           /etc/motd
-COPY ./scripts/entrypoint /usr/local/bin/entrypoint
-COPY ./scripts/guix-check /usr/local/bin/guix-check
-COPY ./scripts/guix-start /usr/local/bin/guix-start
+COPY --from=docker_root ./motd.txt           /etc/motd
+COPY --from=docker_root ./scripts/entrypoint /usr/local/bin/entrypoint
+COPY --from=docker_root ./scripts/guix-check /usr/local/bin/guix-check
+COPY --from=docker_root ./scripts/guix-start /usr/local/bin/guix-start
 
 # Create directory for mounting and grant necessary permissions
 RUN mkdir -p /src/dash && \

contrib/containers/guix/docker-compose.yml

@@ -2,8 +2,10 @@ version: "3.9"
 services:
   guix_ubuntu:
     build:
-      context: '.'
-      dockerfile: './Dockerfile'
+      context: '../../..'
+      additional_contexts:
+        - docker_root=.
+      dockerfile: './contrib/containers/guix/Dockerfile'
       args:
         USER_ID: 1000   # set this to $(id -u) of the host
         GROUP_ID: 1000  # set this to $(id -g) of the host