Compiled external module, Exec format error

I tried to compile wireguard from source in armbian xenial with kernel 4.9.7. on a Banana Pro.

After compiling and installing the resulting kernelmodule, modprobe fails:

sudo modprobe wireguard

modprobe: ERROR: could not insert 'wireguard': Exec format error

dmesg shows:

[ 5563.012529] wireguard: loading out-of-tree module taints kernel.

[ 5563.013912] wireguard: unknown relocation: 102

On the wireguard list, one pointed out this might be related to old toolchain, so i checked:

the installed gcc is:

gcc version 5.4.0 20160609 (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.4) 

and the mentiond gcc Version in dmesg is

 (gcc version 6.2.1 20161016 (Linaro GCC 6.2-2016.11) )

So do i need to crosscompile the module? I set up a crosscompile enviroment as described in the documentation, but its lacking hints about compiling external kernelmodules.

Regards, Alexander Morlang