Ant plugin doesn't set JAVA_HOME

I’m building a small java application josm and noticed that the ant plugin doesn’t actually set JAVA_HOME at build time. So I had to make a specific build stanza in which I set JAVA_HOME to /usr/lib/jvm/java-8-openjdk-amd64 - making my yaml non-portable. In addition I had to specifically stage the openjdk-8-jdk package for it to find the javac compiler.

Is there any reason the ant snapcraft plugin doesn’t do the “right” thing by setting JAVA_HOME and installing a default JDK?