any Cortex-M compatible debugger with the SWD interface is able to flash and debug the XDK. I mostly use a Jlink Base at work and have also used non-Jlink devices like the iSystem ic2000 and ic5000 tracers. The Energy Micro Giant Gecko Starter Kits(based on Jlink) will also work .
Only Segger jLink powered devices are supported out-of-the-box by the XDK Workbench, so any other solution will require some extra work to get the flashing and debugging to work.
Just be aware to use properly licenced Segger Tools! The EDU edition should work on all Cortex-M devices, but you need to use it in a non-comercial environment.