Here's a page I made many years ago, describing how to repair a broken circuit board (I once repaired a computer keyboard like this with a crack all the way down the center). The technique is the same for bridging over a broken trace (if ever you are intentionally breaking a trace with plans to later re-bridge it, do it next to a solder hole so you don't have to use any wire to re-bridge it).
Repairing Broken Circuit Boards
In summary, use a single strand from stranded copper wire and scratch the coating off the circuit trace to solder on to it.