Making a container: asset precompile issues due to no postgres socket file

[cwant]

Hi all, I've tried running ffcrm via docker compose and through Dokku (Heroku-like PaaS), but each time I try to build the web/app container, I run into issues because there is no connection to PostgreSQL when the container is being build, e.g.,

$ docker compose up

[lots of output related to installing apt packages and gems, then ...]

 > [web 6/6] RUN bundle exec rails assets:precompile:                                                                               
3.459 rails aborted!                                                                                                                
3.459 ActiveRecord::ConnectionNotEstablished: connection to server on socket "/var/run/postgresql/.s.PGSQL.5432" failed: No such file or directory (ActiveRecord::ConnectionNotEstablished)                                                                             
3.459   Is the server running locally and accepting connections on that socket?                                                     

[lots more output due to backtrace]

Just wondering if anybody else has hit this, and if they can suggest a work around?

Cheers,
Chris