There is already a binary early access release build.
There are sources for it, too.
I think, someone should add an ebuild(s) with one or both options to the java-overlay, or even to the main portage repository.
I`ll try to make an ebuild for binary ones, and, possibly, for from-source build, but, disregarding my over 4 years gentoo experience, I`m completely new to writing ebuilds.
So, if some people are working on it, I will appreciate them for acknowledgement.
Otherwise, I`ll try to write and submit some ebuild here within 24 hours.
Related links (build instructions,readme and so on)
Old bug is old.