Ignore build data with docker-compose

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

Dockerfile

@@ -21,6 +21,8 @@ ENV PATH="/root/.cargo/bin:$PATH"
 RUN mkdir /app
 WORKDIR /app
 
+
 RUN mix local.hex --force
+RUN mix local.rebar --force
 
 CMD mix run --no-halt

docker-compose.yml

@@ -5,5 +5,7 @@ services:
     env_file: docker.env
     volumes:
       - ".:/app"
+      # ignore build data
+      - "/app/_build"
     working_dir: "/app"
     restart: always