https://github.com/npinto/sekyfsr-gentoo-overlay/commit/ba5271f1079d887e1cd7df7ba34fd290f35c9e5f
*** Bug 425344 has been marked as a duplicate of this bug. ***
Hello. A link to github is no patch to gx86.. second, there already is prefix support in the overlay. A better approach if you want to help is to diff gx86 and prefix.
Ping @ Nicolas: could you please post a patch against the latest version in gx86.
openexr-2.0.0 looks fine in this regard, assuming fixed.