[Mesa-dev] include faster c++ hash map

[Daniel Schürmann]

Hi,

I would like to know if it would be possible to make mesa
(at least RADV and maybe later radeonSI) depending on
robin-map-dev (https://github.com/Tessil/robin-map) which
seems to be part of some distros, and otherwise could be
just copied into mesa.

And if we could alternatively get a dependency on abseil,
that would be even better.

I could probably also live with an optional dependency,
if someone can explain how this could be expressed
and used in meson.

Some testing showed that it could quite nicely improve
compile speed for ACO.

Kind regards,
Daniel