[FS#1121] make image doesn't return failure if build fails

[LEDE Bugs]

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

User who did this - Brian J. Murrell (brianjmurrell) 

Attached to Project - LEDE Project
Summary - make image doesn't return failure if build fails
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Medium
Priority - Very Low
Reported Version - lede-17.01
Due in Version - Undecided
Due Date - Undecided
Details - Supply the following if possible:
 - Device problem occurs on
N/A

 - Software versions of LEDE release, packages, etc.
17.01.4

 - Steps to reproduce
Set up the imagebuilder and build an image with:


make -C $BUILDER_DIR/ image PROFILE="$PROFILE" PACKAGES="$PACKAGES" FILES="$PWD/$FILES_DIR" CUSTOMIZE_IMAGE_SCRIPT=$PWD/$ROUTER_MODEL.custom
   

Where $PACKAGES is a list big enough to make the image too big so that you get:


[mktplinkfw] *** error: images are too big by 1614 bytes


Observe that the exit status from the above make is still 0.  That make should reflect that the build failed with a non-zero exit status.

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1121