Dê uma olhada nos detalhes sobre como compilar os drivers MadWifi para outras arquiteturas. Tal como no seu caso, você está tentando compilar para o ARM4, embora talvez não intencionalmente.
trecho
Cross-compiling
The build system is designed to support cross-compiling without any modification to the distribution files. It should be sufficient to specify any parameters on the make command line.
In most cases, only KERNELPATH and CROSS_COMPILE need to be defined. CROSS_COMPILE is the prefix for cross-compiling tools. For instance, if the cross compiler is called arm-linux-gcc, set CROSS_COMPILE to "arm-linux-":
$ make KERNELPATH=/usr/src/linux-arm CROSS_COMPILE=arm-linux-
The build system determines ARCH and TARGET based on the .config file in the Linux build tree. TARGET still may need to be provided on the command line some uncommon systems. If ARCH is determined incorrectly, please report it.