[FS#1063] imagebuilder: show IMAGE_SIZE in `make info`

[LEDE Bugs]

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

User who did this - aparcar (aparcar) 

Attached to Project - LEDE Project
Summary - imagebuilder: show IMAGE_SIZE in `make info`
Task Type - Feature Request
Category - Toolchain
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Low
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - It would be very handy to know the max image size possible for devices. 

Instead of parsing e.g. https://lede-project.org/toh/start manually it would be handy to add this capability to all imagebuilders itself. 

A Value of 0 could be used as no limitation (as for x86/64).



More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1063