Ignore the AlternateLBA field in the GPT headers.

src/platform/vboot_reference/utility/cgpt/cgpt_options.c

 /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  * Update GPT attribute bits.
  */
 #include <getopt.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ skipping 107 matching lines @@
         return CGPT_FAILED;
       }
     }
   }
   return CGPT_OK;
 }
 
 int OpenDriveInLastArgument(const int argc,
                             char *const *argv,
                             struct drive *drive) {
-  /* Then, we need a non-option argument. */
-  if (optind == (argc - 1)) {
-    char *path, drive_path[256];
-    path = argv[optind];
-    switch (path[0]) {
-      case '.':
-      case '/':
-        snprintf(drive_path, sizeof(drive_path), "%s", path);
-        break;
-      default:
-        snprintf(drive_path, sizeof(drive_path), "/dev/%s", path);
-        break;
-    }
-    if (CGPT_OK != DriveOpen(drive_path, drive)) {
-      printf("[ERROR] DriveOpen(%s) error!\n", drive_path);
-      return CGPT_FAILED;
-    }
-  } else {
+  if (optind != (argc - 1)) {
     printf("[ERROR] One (and only one) non-option argument is required.\n");
     return CGPT_FAILED;
   }
 
-  return CGPT_OK;
+  return DriveOpen(argv[optind], drive);
 }