Merge pull request #121 from batmat/enable-jdk11

Build on various platforms for compat checking

Jenkinsfile

@@ -1 +1,10 @@
-buildPlugin(useAci: true)
+buildPlugin(useContainerAgent: true,
+        configurations: [
+                [platform: 'linux', jdk: '11'],
+                [platform: 'windows', jdk: '8'],
+
+                // testing the Guava & Guice bumps
+                // https://github.com/jenkinsci/jenkins/pull/5707
+                // https://github.com/jenkinsci/jenkins/pull/5858
+                [ platform: "linux", jdk: "8", jenkins: '2.321', javaLevel: "8" ]
+        ])