[dist] Setup some convenience binaries

Put some links to the 'right' ruby/gem/irb binaries into $PATH.
Makes it easier for people who exec/run the frontend container.

Dockerfile.frontend-base

@@ -32,8 +32,16 @@ RUN chown -R frontend /obs/src/api
 # builds this container
 USER frontend
 WORKDIR /obs/src/api
-RUN export NOKOGIRI_USE_SYSTEM_LIBRARIES=1; bundle install --jobs=3 --retry=3
 
+# Set up some convenience ruby binaries...
+RUN for i in ruby gem irb; do ln -s /usr/bin/$i.ruby2.4 ~/bin/$i; done
+
+# Install our bundle
+# FIXME: Retrying bundler if it fails is a workaround for https://github.com/moby/moby/issues/783
+#        which seems to happen on openSUSE (< Tumbleweed 20171001)...
+RUN export NOKOGIRI_USE_SYSTEM_LIBRARIES=1; bundle install --jobs=3 --retry=3 || bundle install --jobs=3 --retry=3
+
+# Switch to root again so we don't block changing our frontend user id...
 USER root
 
 # Run our command