Made tnl-cuda-arch more robust

#include <stdio.h> 

int main() {

    int num_devices;

    cudaGetDeviceCount( &num_devices );

    int num_devices = 0;

    cudaError_t error_id = cudaGetDeviceCount( &num_devices );

    if( error_id != cudaSuccess ) {

        fprintf(stderr, "cudaGetDeviceCount returned error %d (%s)\n",

                (int) error_id, cudaGetErrorString(error_id));

        exit(EXIT_FAILURE);

    }

    for( int i = 0; i < num_devices; i++ ) {

        cudaDeviceProp prop;

        cudaGetDeviceProperties( &prop, i );