keep at least 1 cpu core for heterogeneous tests

starpurm/dev/cuda_vector_scale/vector_scale.c

@@ -238,12 +238,15 @@ int main(int argc, char *argv[])
 
 	if (rm_nb_cpu_units > 1 && rm_nb_cuda_units > 1)
 	{
-		const int nb_cpus = rm_nb_cpu_units;
+		int nb_cpus = rm_nb_cpu_units;
 		const int nb_cudas = rm_nb_cuda_units;
 		const int cuda_type = rm_cuda_type_id;
 		printf("nb_cpu_units = %d\n", nb_cpus);
 		printf("nb_cuda_units = %d\n", nb_cudas);
 
+		/* Keep at least one CPU core */
+		nb_cpus--;
+
 		starpurm_set_drs_enable(NULL);
 		drs_enabled = starpurm_drs_enabled_p();
 		assert(drs_enabled != 0);