Keil-MDK supports DWARF 4 debug information since version 5.35. You can compile with the -gdwarf-4 option to debug with Arm Debugger. However, if you are using legacy or third-party tools that do not support DWARF 4 debug information, you can specify the level of DWARF conformance required using the -gdwarf-2 or -gdwarf-3 options.
You can check in https://review.trustedfirmware.org/#/c/trusted-firmware-m/+/1532/ rooftop snipers