you can not compile fgear plugin right away like that, you are using the binaries compiled by epic games. to compile the plugin yourself you need to create a C++ project and include fgear files manually to create an additional plugin project. this is not a simple task that i can teach you with instructions, you need to be experienced in C++ in general. my recommendation for you is to develop your own ai code in BP, maybe you can try to convert the auto drive component code to BP.