gallium: add a non-multisample sample mask out behaviour flag.

Vulkan/DX want to use output sample mask even when not multisampling
GL wants it ignored.

Add a rasterizer flag to lavapipe can get correct behaviour.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7435>
1 file changed