Make sure that config->topology.nhwcpus is always set to 1.

src/drivers/cpu/driver_cpu.h

@@ -36,7 +36,9 @@ int _starpu_cpu_driver_run_once(struct starpu_driver *);
 int _starpu_cpu_driver_deinit(struct starpu_driver *);
 void _starpu_cpu_discover_devices(struct _starpu_machine_config *config);
 #else
-#define _starpu_cpu_discover_devices(config) ((void) config)
+#define _starpu_cpu_discover_devices(config) do { \
+	(config)->topology.nhwcpus = 1; \
+} while (0)
 #endif /* !STARPU_USE_CPU */
 
 #endif //  __DRIVER_CPU_H__