build.sh: Sort package-srcuris.txt (v5.1.2)

:Release Notes:
Sort package-srcuris.txt retained as build artifact.

:Detailed Notes:

:Testing Performed:
Only build tested.

:QA Notes:
No change to image.

:Issues Addressed:
[ES-958] Sort package-srcuris.txt retained as build artifact

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>
Change-Id: Ib10a9e70297821790775ab25f7d1aa7a98b50e91
Reviewed-on: https://g2g.palm.com/6383
Reviewed-by: DCO Verification
Reviewed-by: Susan Montooth <susan.montooth@lge.com>
Tested-by: Susan Montooth <susan.montooth@lge.com>