Add the "STEAL" target from the "demos" branch

extensions/Kbuild

@@ -12,6 +12,7 @@ obj-${build_ECHO}        += xt_ECHO.o
 obj-${build_IPMARK}      += xt_IPMARK.o
 obj-${build_LOGMARK}     += xt_LOGMARK.o
 obj-${build_SYSRQ}       += xt_SYSRQ.o
+obj-${build_STEAL}       += xt_STEAL.o
 obj-${build_TARPIT}      += xt_TARPIT.o
 obj-${build_TEE}         += xt_TEE.o
 obj-${build_condition}   += xt_condition.o