Use Jenkins base image to avoid workaround for Docker packaging limit…

…ations

Dockerfile

@@ -1,31 +1,16 @@
-FROM jenkins/jenkins:2.176.2 as install_scripts_source
+FROM cloudbees/cloudbees-jenkins-distribution:2.176.2.3 as war_source
 
-FROM cloudbees/cloudbees-jenkins-distribution:2.176.2.3
-COPY --from=install_scripts_source /usr/local/bin/jenkins-support /usr/local/bin/jenkins-support
-COPY --from=install_scripts_source /usr/local/bin/install-plugins.sh /usr/local/bin/install-plugins.sh
-
-ENV JENKINS_UC http://jenkins-updates.cloudbees.com
-ENV JENKINS_INCREMENTALS_REPO_MIRROR https://repo.jenkins-ci.org/incrementals
-
-# Workaround https://github.com/jenkinsci/docker/issues/857
-USER root
-RUN mkdir -p /usr/share/jenkins/ && ln -s /usr/share/cloudbees-jenkins-distribution/cloudbees-jenkins-distribution.war /usr/share/jenkins/jenkins.war
-USER cloudbees-jenkins-distribution
+FROM jenkins/jenkins:2.176.2
+COPY --from=war_source /usr/share/cloudbees-jenkins-distribution/cloudbees-jenkins-distribution.war /usr/share/jenkins/jenkins.war
 
 # Startup all plugins included into the CloudBees Jenkins Distribution bundle
 ENV JAVA_OPTS "-Dcom.cloudbees.jenkins.cjp.installmanager.CJPPluginManager.allRequired=true"
 
-# Install extra plugins
-# REF_ROOT is consumed by jenkins-support in the https://github.com/jenkinsci/docker/issues/861 workaround
-ENV REF_ROOT=/usr/share/cloudbees-jenkins-distribution/ref
-ENV REF=${REF_ROOT}/plugins
-COPY plugins.txt /usr/share/cloudbees-jenkins-distribution/ref/plugins.txt
-RUN bash /usr/local/bin/install-plugins.sh < /usr/share/cloudbees-jenkins-distribution/ref/plugins.txt
+# Install additional plugins including JCasC
+ENV JENKINS_UC http://jenkins-updates.cloudbees.com
+COPY plugins.txt /usr/share/jenkins/ref/plugins.txt
+RUN bash /usr/local/bin/install-plugins.sh < /usr/share/jenkins/ref/plugins.txt
 
-# Apply JCasC
+# Apply JCasC configuration
 COPY jenkins.yaml /cfg/jenkins.yaml
 ENV CASC_JENKINS_CONFIG /cfg/jenkins.yaml
-
-# Temporary override for jenkins-support to support custom ref-roots there
-# TODO: remove once https://github.com/jenkinsci/docker/issues/861 is fixed
-COPY jenkins-support /usr/local/bin/jenkins-support