Add a Jenkinsfile for building

Jenkinsfile

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+/*
+ * This is a multibranch workflow file for defining how this project should be
+ * built, tested and deployed
+ */
+
+def nodeLabel = 'java'
+
+node(nodeLabel) {
+    stage 'Clean workspace'
+    /* Running on a fresh Docker instance makes this redundant, but just in
+     * case the host isn't configured to give us a new Docker image for every
+     * build, make sure we clean things before we do anything
+     */
+    deleteDir()
+
+
+    stage 'Checkout source'
+    /*
+     * Represents the SCM configuration in a "Workflow from SCM" project build. Use checkout
+     * scm to check out sources matching Jenkinsfile with the SCM details from
+     * the build that is executing this Jenkinsfile.
+     *
+     * when not in multibranch: https://issues.jenkins-ci.org/browse/JENKINS-31386
+     */
+    checkout scm
+
+
+    stage 'Build and test'
+    /* if we can't install everything we need for Ruby in less than 15 minutes
+     * we might as well just give up
+     */
+    timeout(30) {
+        sh './gradlew -iS'
+    }
+}
+
+// vim: ft=groovy