Use custom Ruby images to test builds

It allows us to remove redundant steps of installing required dependencies for every build.

.gitlab-ci.yml

-image: "ruby:2.3.1"
+image: "registry.gitlab.com/gitlab-org/gitlab-build-images:ruby-2.3"
 cache:
   key: "ruby-231"
@@ -141,7 +141,7 @@ spinach 9 10: *spinach-knapsack
 # Execute all testing suites against Ruby 2.1
 .ruby-21: &ruby-21
-  image: "ruby:2.1"
+  image: "registry.gitlab.com/gitlab-org/gitlab-build-images:ruby-2.1"
   <<: *use-db
   only:
     - master

CHANGELOG

@@ -882,6 +882,7 @@ v 8.9.0
   - Add API endpoint for Sidekiq Metrics !4653
   - Refactoring Award Emoji with API support for Issues and MergeRequests
   - Use Knapsack to evenly distribute tests across multiple nodes
+  - Use custom Ruby images to test builds (registry.gitlab.com/gitlab-org/gitlab-build-images:*)
   - Add `sha` parameter to MR merge API, to ensure only reviewed changes are merged
   - Don't allow MRs to be merged when commits were added since the last review / page load
   - Add DB index on users.state

scripts/prepare_build.sh

@@ -16,21 +16,6 @@ retry() {
 }
 if [ -f /.dockerenv ] || [ -f ./dockerinit ]; then
-    mkdir -p vendor/apt
-
-    # Install phantomjs package
-    pushd vendor/apt
-    PHANTOMJS_FILE="phantomjs-$PHANTOMJS_VERSION-linux-x86_64"
-    if [ ! -d "$PHANTOMJS_FILE" ]; then
-        curl -q -L "https://s3.amazonaws.com/gitlab-build-helpers/$PHANTOMJS_FILE.tar.bz2" | tar jx
-    fi
-    cp "$PHANTOMJS_FILE/bin/phantomjs" "/usr/bin/"
-    popd
-
-    # Try to install packages
-    retry 'apt-get update -yqqq; apt-get -o dir::cache::archives="vendor/apt" install -y -qq --force-yes \
-      libicu-dev libkrb5-dev cmake nodejs postgresql-client mysql-client unzip'
-
     cp config/database.yml.mysql config/database.yml
     sed -i 's/username:.*/username: root/g' config/database.yml
     sed -i 's/password:.*/password:/g' config/database.yml