Working proof of concept in linux with AdoptOpenJDK 11.

As part of processing#5750 / processing#5753, example sketch and PDE running in Linux with Elementary 5.0 (Juno, 64bit). Linux 4.15.0-36-generic. Specifically, resolved issue with java path on linux given new JDK structure.

build/build.xml

@@ -899,7 +899,7 @@
     </condition>
 
     <!-- Force full JDK when not on train 1 (force when on java 11) -->
-    <condition property="jre.dir" value="jdk-${jdk.esoteric}+${jdk.build}">
+    <condition property="jre.dir" value="jdk-${jdk.esoteric}+${jdk.build}/">
       <not>
         <equals arg1="${jdk.train}" arg2="1" />
       </not>