docs/releasing: drop custom LLVM_CONFIG if previously manually set

Cc: Emil Velikov <emil.velikov@collabora.com>
Cc: Eric Engestrom <eric.engestrom@imgtec.com>
Signed-off-by: Andres Gomez <agomez@igalia.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
1 file changed