This will link functions combining multiple shaders from the same stage
into a single shader. Unlike alot of the glsl ir linker that has been
converted to NIR the logic here is completely different from the glsl ir
code that linked functions. The existing nir cloning code allows us to
implement this functionality in a much more eligant way than what glsl
ir was doing.
Acked-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31137>
