build-images.yml: fix "." resolution for docker-compose files

docker compose config -f with multiple docker compose files
uses the path of first compose file to resolve ".".
But we want to build all the docker images defined with docker compose in this repo,
thus we call docker compose config for all docker-compose files and merge the service
definitions.

.github/workflows/build-images.yml

@@ -72,14 +72,13 @@ jobs:
         run: |
           set -x
           sudo snap install yq
-          
-          compose_paths=""
-          for i in $(find . -name docker-compose.yml); do 
-             compose_paths="$compose_paths -f $i"
-          done
 
           export REPO_NAME=$(basename $(pwd))
-          docker compose $compose_paths config > /tmp/docker-compose.yml
+          echo "services:" > /tmp/docker-compose.yml
+          for i in $(find . -name docker-compose.yml); do
+             docker compose -f $i config | yq .services | sed 's/^/  /' >> /tmp/docker-compose.yml
+          done
+
           yq_pipe='.services.[]'
           yq_pipe=$yq_pipe'| select(.build != null)'
           yq_pipe=$yq_pipe'| [.build * {"image": .image}]'