Merge branch 'add-ubuntu-20-04-focal' into 'master'

Add Ubuntu 20.04 build image

See merge request gitlab-org/gitlab-build-images!304

.gitlab-ci.yml

@@ -98,6 +98,7 @@ omnibus-gitlab-opensuse15.1 test: *test_build
 omnibus-gitlab-stretch test: *test_build
 omnibus-gitlab-buster test: *test_build
 omnibus-gitlab-xenial test: *test_build
+omnibus-gitlab-focal test: *test_build
 omnibus-gitlab-depscan test: *test_build
 omnibus-gitlab-cve-search test: *test_build
 
@@ -157,6 +158,7 @@ omnibus-gitlab-opensuse15.1: *build_and_deploy
 omnibus-gitlab-stretch: *build_and_deploy
 omnibus-gitlab-buster: *build_and_deploy
 omnibus-gitlab-xenial: *build_and_deploy
+omnibus-gitlab-focal: *build_and_deploy
 omnibus-gitlab-depscan: *build_and_deploy
 omnibus-gitlab-cve-search: *build_and_deploy
 release-tools: *build_and_deploy

Dockerfile.omnibus-gitlab-focal

+FROM ubuntu:20.04
+
+RUN apt-get update -q \
+        && apt-get install -y g++ gcc git make curl zlib1g-dev libssl-dev locales \
+        && apt-get autoremove -yq \
+        && apt-get clean -yqq \
+        && rm -rf /var/lib/apt/lists/*
+
+RUN echo "en_US.UTF-8 UTF-8" > /etc/locale.gen
+RUN locale-gen en_US.UTF-8
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
+
+ENV RUBY_VERSION 2.6.5
+RUN curl -fsSL "https://cache.ruby-lang.org/pub/ruby/2.6/ruby-${RUBY_VERSION}.tar.gz" \
+  | tar -xzC /tmp \
+  && cd "/tmp/ruby-${RUBY_VERSION}" \
+  && ./configure --disable-install-rdoc --disable-install-doc --disable-install-capi\
+  && make \
+  && make install \
+  && cd / \
+  && rm -rf "/tmp/ruby-${RUBY_VERSION}" \
+  && gem install bundler --no-document