010b2f9497
This adds explicit names for softpipe and llvmpipe to the gallium driver list. "swrast" is treated as a compatibility name that selects both. We clarify how lavapipe depends on (just) llvmpipe, and we make it possible to build llvmpipe without softpipe. Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27607>