Ok, I'm starting to work on migrating mesa. A few notes so far: 1. libclc seems to be ABI-agnostic. Yet it installs pkg-config file to totally invalid directory (bug 476650). If I'm right, we'll make it use /usr/share/pkgconfig and submit that upstream. 2. mesa[xorg] requires xorg-server.pc. Symlinking it along with fontsproto to lib32/pkgconfig seems to work. Therefore, we'll probably need to make a multilib xorg-server with includes being the only multilib thing. I expect this to be the hardest part. 3. I have no idea how mesa interfaces eselect-opengl (did I mention already we should kill this eselect aberration?).
chithead told me that we mesa[xorg] is pointless for multilib, so it got far easier. You can see my current work on 'multilib-opengl' branch of x11 overlay.
Equally this has all been in the FireBurn overlay for a very long time
The multilib branch was merged into the x11 overlay master branch.
Now you should apply the in-tree patch since it addresses the packages that aren't in x11 overlay. Otherwise, it's not really beneficial since it's a blocker for emul-linux.
Seems like, at least it works fine for me, FireBurn overlay got solution for blocking emul packages and I see maintainer right in this bug. What about review it?
Committed p.masked for testing.