When using disk_layout files but not config file, we autofill the harddrives argument (#1067)

archinstall/__init__.py

@@ -230,6 +230,8 @@ def post_process_arguments(arguments):
 		if not json_stream_to_structure('--disk_layouts',arguments['disk_layouts'],layout_storage):
 			exit(1)
 		else:
+			if arguments.get('harddrives') is None:
+				arguments['harddrives'] = [disk for disk in layout_storage]
 			# backward compatibility. Change partition.format for partition.wipe
 			for disk in layout_storage:
 				for i,partition in enumerate(layout_storage[disk].get('partitions',[])):