Fix UID/GID update for codespaces-linux smoke test

Author: Chuxel

.github/actions/smoke-test/action.yaml

@@ -69,20 +69,25 @@ runs:
         fi
 
         set -e
-        
-        # Start container
-        container_name="vscdc-test-container"
-        docker run -d --name ${container_name} --rm --init --privileged -v "$(pwd)/containers/${{ inputs.definition }}:/workspace" ${{ inputs.image }} /bin/sh -c 'while sleep 1000; do :; done'
 
         # Update UID/GID for user in container - Actions uses different UID/GID than container
         # which causes bind mounts to be read only and cause certain write tests to fail
         # The dev container CLI handles this automatically but we're not using it.
         local_uid=$(id -u)
         local_gid=$(id -g)
-        echo "(*) Update container user UID/GID..."
-        docker exec -u root ${container_name} /bin/sh -c "\
-          groupmod -g ${local_gid} ${{ inputs.user }} \
-          && usermod -u ${local_uid} -g ${local_gid} ${{ inputs.user }}"
+        echo "(*) Updating container user UID/GID..."
+        echo -e "FROM ${{ inputs.image }}\n \
+          RUN export sudo_cmd="" \
+            && if [ "$(id -u)" != "0" ]; then export sudo_cmd=sudo; fi \
+            && \${sudo_cmd} groupmod -g ${local_gid} ${{ inputs.user }} \
+            && \${sudo_cmd} usermod -u ${local_uid} -g ${local_gid} ${{ inputs.user }}" > uid.Dockerfile
+        cat uid.Dockerfile
+        docker buildx build --load -t ${{ inputs.image }}-uid -f uid.Dockerfile .
+
+        # Start container
+        echo "(*) Starting container..."
+        container_name="vscdc-test-container"
+        docker run -d --name ${container_name} --rm --init --privileged -v "$(pwd)/containers/${{ inputs.definition }}:/workspace" ${{ inputs.image }}-uid /bin/sh -c 'while sleep 1000; do :; done'
 
         # Fake out existence of extensions, VS Code Server
         echo "(*) Stubbing out extensions and VS Code Server..."