radeonsi: use build-id when available for disk cache

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
(cherry picked from commit 2169acbf)
[Juan A. Suarez: resolve trivial conflicts]
Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>

Conflicts:
	src/gallium/drivers/radeonsi/si_pipe.c