yes its probably related to a gcc version mismatch, install the gcc your kernel was compiled with and recompile the module export CC=/path/to/gcc/you/want/to/use
also did you notice in the error
You must change your working directory to /lib/modules/fglrx
and then call ./make_install.sh in order to install the built module.
have you done that step?
and john deere sucks, get a case!! hehe jk