Stop using multiple dockerfiles and start specifying targets for multi-stage builds

[falgon]

• The following two:
  • https://github.com/falgon/roki-web/blob/76bb34fbfd74c2de891cc42cfc965b117fbed95f/docker/contents/Dockerfile
  • https://github.com/falgon/roki-web/blob/76bb34fbfd74c2de891cc42cfc965b117fbed95f/docker/dev/Dockerfile

• Make multi-stage builds happen within the Dockerfile, eg.

  FROM ubuntu:24.03 AS base
  # Install dependencies from apt and setup ghcup (do not forget to get chromium browser...)
  
  # for development...
  FROM base AS dev
  WORKDIR /src
  RUN --mount=type=bind,source=.,dst=.,rw \
      stack --no-terminal --allow-different-user build --only-dependencies
  
  # build stage (for app)
  FROM dev AS build
  WORKDIR /src
  RUN --mount=type=bind,source=.,dst=.,rw \
      mkdir /dist && stack --no-terminal --allow-different-user install --local-bin-path /dist
  
  # for site and spa
  FROM alpine:latest AS apps
  WORKDIR /app
  RUN apk update && apk upgrade --no-cache && apk add --no-cache gmp-dev libffi-dev zlib-dev chromium
  COPY --from=build /dist/site /app/site
  COPY --from=build /dist/spa /app/spa
  ENV PATH /app:$PATH
  EXPOSE 8888

  docker-compose.yml, eg.

  services:
      build:
          image: $ROKI_WEB_ENV_IMAGE_NAME $ROKI_WEB_ENV_IMAGE_TAG
          container_name: roki-web-build
          volumes:
              - "../contents:/home/rw-c/bin/contents"
          ports:
              - "8888:8888"
          working_dir: /home/rw-c/bin
          build:
              context: ../
              dockerfile: ./Dockerfile
              target: apps # important
          command: site build --preview
      preview:
          # ditto...
          build:
              context: ../
              dockerfile: ./Dockerfile
              target: apps
          command: site watch --preview --port 8888 --host 0.0.0.0
  # ditto...