[JENKINS-54064] Bundle classes as JAR file into HPI file
[JENKINS-54064] Bundle classes as JAR file into HPI file

In version 0.36.0 of the jpi plugin bundling the classes has been changed.
Instead of putting them into the HPI file under WEB-INF/classes/, they are
now put into a JAR file under WEB-INF/lib/. This is required for Jenkins
JAR file prefetching & caching to work properly (see JENKINS-15120).

jenkinsci/ivy-plugin,jenkinsci/ivy-plugin