Modification firmware

Hello! Let me explain my situation. I have a 2016 Nissan Leaf Azeo 30kWh. I had the OVMS module and everything worked perfectly. However, since I upgraded the Leaf to 62kWh, the SOC (State of Charge) no longer appears. I noticed that the OVMS uses message 1DB to evaluate the SOC, but my 62kWh BMS doesn't send this message. I had to modify the firmware, specifically vehiclenissanleaf.cpp, so that the OVMS could read the SOC on message 05BC. The problem is that I can't get it to build. Could you please provide me with the procedure? Thank you very much. Sincerely, Cyril