http://c25o7knygjm3m67jy27yuynvv4pkfi25naucscmh4ubq2ggiig3v57ad.onion/en/supporting-java-modules-in-guix.html
Third, since we still use Java 8 by default, all builds that use Java 8 (that
is, the vast majority of Java packages) initially failed since Java 8 doesn't
support the modulepath option. Making it optional via a build-system argument
solved the issue. To build with modules and the ant-build-system , you need
to do: (arguments
`(#:jdk ,openjdk9; or later
#:use-java-modules?