How would you give cpr to someone who may have a broken neck?

See below. In someone with no pulse and no breathing, CPR takes priority over everything else, otherwise the person will die. If you suspect trauma to the neck there are techniques to administer CPR without moving the neck. This is discussed in every basic life support course which is a great thing to take.
If you have help. Have a second person merely place their hands on both sides of the victims head from the head end to stabilize the head and neck until help arrives. Do compression only CPR until ems rescue arrives.