about build SYS

[51819]

I ues 19949 XIP +19400 SYS to diy a rom!
i know the rom ce os 19949 (Build 19400)!

now,i have a question! how to do [ce os 19949 (Build 19400)]-->[ce os 19949 (Build 19949)], when have not 19949 SYS?