mattia@chase ~ % apt-file search /usr/lib/jvm/default-java
default-jre-headless: /usr/lib/jvm/default-java
Indeed adding it to build-deps the package builds.
Make sure to do your test builds inside a clean chroot.
BTW, I don't see an update package on mentors (if you meant to upload
one). I can't do much if I can't see what you've done till now :)