specfile: only declare utils if we build it

Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Signed-off-by: Philippe DENIEL <philippe.deniel@cea.fr>
FSAL_LUSTRE: builds FSAL_SHOOK with name "SHOOK"

Signed-off-by: Philippe DENIEL <philippe.deniel@cea.fr>