See https://bugs.openjdk.java.net/browse/JDK-8023279 for a description of the problem. On the FX side we need to generate a javafx-ext-meta-index file and export it as part of the cobundle exports produced by the FX build for inclusion into the JDK build. The JDK build will take the contents of this file and concatenate it to jre/lib/ext/meta-index.