JIMRI/java/graalvm

We can't now require everybody to install a GraalVM JDK, so we have a workaround:

• This java/graalvm directory contains GraalVM-specific code that requires a GraalVM JDK to build.
• The code lives in the jmri.script.jsr223graalpython package
  • Eventually, this source will move to java/src/jmri/script/jsr223graalpython
• To let JMRI run without building in the meantime, we distribute this code in a lib/jmri.script.jsr223graalpython.jar file

To recreate that jar file to e.g. use updates you've made locally:

ant graal-compile
cd target/graalvm-classes
jar cf ../../lib/jmri.script.jsr223graalpython.jar .
cd ../..