[FS#370] Unable to do upgrade from a system built by image builder

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - EdiTurn (EdiTurn) 

Attached to Project - LEDE Project
Summary - Unable to do upgrade from a system built by image builder
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - High
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - The device I'm using: Netgear WNDR4300

Problem: If the current system is built by image builder, it's unable to do system upgrade. Everything remains unchanged after reboot. 
 
At this present, a system image build by image builder is different from the pre-compiled firmware from website. It lacks of 3 packages: iwinfo, libiwinfo and ubi-utils. The missing of ubi-utils do cause this problem. 

According to this commit (https://git.lede-project.org/?p=source.git;a=commitdiff;h=9352603fff591a2412fb825aa2f5ef386990c99a), the package ubi-utils has been merged to a new package mtd-utils and is not available in the repository any longer. However the new package mtd-utils can not be found in the repository either.  

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=370