First of all, Hacking at its most basic does not even require a computer. Hackers actually predate the Personal Computer. Hacking means using something in an unintended way, to gain a benefit for yourself that you should not be able to get otherwise.
Second the term life-hack has apparently replaced the term we used to use, common sense. Or finding the easy way to do something. Of course most people use life hack to mean finding a much more difficult but creative way to achieve a goal.