1EMPTY= 2 3check-empty: 4 @${MAKE} -f ${MAKEFILE} do-$@ 5 @${MAKE} -f ${MAKEFILE} -j2 do-$@ 6 @${MAKE} -f ${MAKEFILE} -j2 -B do-$@ 7 8do-check-empty: 9 ${EMPTY} 10 @${EMPTY} 11 @-${EMPTY} 12