Penny for your thoughts, guys: I am thinking about splitting the
video_cards_i965 condition in virtual/opencl so that NEO is pulled in by
video_cards_iris instead, and I wonder if there is anything I haven't
thought about.

The reason why I would like to do this is that there is clear
correspondence between compatibility matrices of the Iris OpenGL driver
and the NEO OpenCL driver - both only work on Broadwell and newer. There
are differences of course, most notably that the old OpenCL driver
(Beignet) is already considered deprecated for systems supported by NEO
whereas the old OpenGL driver in Mesa (i965) is still the official one
even for newer systems.

Nb. to the best of my knowledge it is safe to set VIDEO_CARDS=iris even
globally because if both i965 and iris are available, Mesa for now still
prefers the former unless the environment variable
MESA_LOADER_DRIVER_OVERRIDE has been set to 'iris'.

There would of course have to be a news item advising the users of
virtual/opencl + dev-libs/intel-neo to adjust their USE flags.

What do you think, guys?

-- 
Marecki