Mesa out of date (and move to libglvnd?)

[John Kehayias]

Hi everyone,

Mesa has fallen quite of date (latest upstream is 21.1.4, guix core-updates up 
to 20.2.6, or else 20.2.4 for everyone else). There is patch available here: 
https://issues.guix.gnu.org/49339 however it currently includes enabling 
libglvnd. I don't think that is necessary from my testing, but does raise the 
question of moving to libglvnd for packages requiring GL (which would be needed 
if Mesa has it enabled).

As far as I understand it, libglvnd is meant to be vendor neutral and provide 
GL for anything to link to, and then hands off to vendor specific GL. I have at 
tested building some packages when mesa has libglvnd enabled, like libepoxy and 
xorg-server. Both needed libglvnd as inputs, but otherwise build fine. I 
haven't tested running as I'm currently on a foreign distro. However, does seem 
like this would be a good idea, as it should alleviate dealing with vendor 
specific GL in building packages. libglvnd is new to me, but perhaps someone 
can weigh in on this issue?

Anyway, my main goal right now is to have Mesa updated in core-updates before 
the upcoming freeze. Mesa is already very out of date, and would then push it 
to another ~6 months for the next core-updates when it is already ~7 months out 
of date (and they make quick releases for fixes in drivers and software that 
uses Mesa).

I can update #49339 with a minimal Mesa version bump patch if that helps, just 
don't want it to get lost in the current shuffle.

Thanks!
John