Java 9 : Illegal reflective access by Groovy warnings due to GROOVY-8339

@pmouawad ([Bug 62064](https://bz.apache.org/bugzilla//show_bug.cgi?id=62064&redirect=false)):
WARNING: Illegal reflective access by com.bulenkov.iconloader.util.UIUtil (file:/data/jmeter/jmeters/apache-jmeter-4.0/lib/darcula.jar) to field sun.awt.CGraphicsDevice.scale
WARNING: Illegal reflective access by org.codehaus.groovy.reflection.CachedClass (file:/data/jmeter/jmeters/apache-jmeter-4.0/lib/groovy-all-2.4.13.jar) to method java.lang.Object.finalize()
WARNING: Illegal reflective access by org.codehaus.groovy.reflection.CachedClass (file:/data/jmeter/jmeters/apache-jmeter-4.0/lib/groovy-all-2.4.13.jar) to method java.lang.Object.clone()
WARNING: Illegal reflective access by org.codehaus.groovy.reflection.CachedClass (file:/data/jmeter/jmeters/apache-jmeter-4.0/lib/groovy-all-2.4.13.jar) to method java.lang.Object.registerNatives()
WARNING: Illegal reflective access by org.codehaus.groovy.vmplugin.v7.Java7$1 (file:/data/jmeter/jmeters/apache-jmeter-4.0/lib/groovy-all-2.4.13.jar) to constructor java.lang.invoke.MethodHandles$Lookup(java.lang.Class,int)

This is due to:
https://issues.apache.org/jira/browse/GROOVY-8339

Severity: normal
OS: All