FIX: Use bundle config instead of deprecated flags...

FIX: Use bundle config instead of deprecated flags (https://github.com/discourse/discourse_docker/commit/7ba8d4e926055d0b88b789801f1836d118e309ef)

Dockerfile

@@ -110,10 +110,10 @@ RUN \
     git clone --depth=1 https://github.com/discourse/discourse-graphviz.git /discourse/plugins/discourse-graphviz
 
 ### Gem installation
-RUN exec bundle config --local deployment true &&\
-    exec bundle config --local path ./vendor/bundle &&\
-    exec bundle config --local without test development &&\
-    exec bundle install --jobs 4 &&\
+RUN bundle config --local deployment true && \
+    bundle config --local path ./vendor/bundle && \
+    bundle config --local without test development && \
+    bundle install --jobs 4 && \
     # Do not install yarn as root, it comes from the base image.
     yarn cache clean && \
     exec bundle exec rake maxminddb:get && \