The ebuilds provided by the oomidi overlay have several problems causing them not to work. This ebuild works correctly, not to mention compiles Openoctave noticeably faster.
Created attachment 329624 [details]
Ebuild. Use in local overlay until/unless adopted by pro-audio or oomidi.
Also, the 9999 ebuild in the pro-audio overlay doesn't work because it doesn't seem to reference a working GIT repo any more.
CC'ed proaudio and sound herd in case they are interested
otherwise you can contact the sunrise developers in #gentoo-sunrise and propose your ebuild for inclusion there (sunrise is the official user overlay, everyone can contribute, but needs to pass a review on intial commit)