Error Compiling Building For ArduPilot Mega 2.x

I used github to download a code for my ArduPilot Arudino and i tried to compile but it shows
error compiling
Buidling for ArduPilot Mega 2.X
Excluding arduino core from include paths.
The HAL board i chose ArduPilot Mega 2.X
The board i choise Arduino Mega 2560