DO NOT MERGE: Only use a fixed timestamp when packaging.

This CL changes to use a fixed timestamp only when packaging
into the target_files zip.

Bug: 24377993
Change-Id: I01d136f4b99e1eff80c559192d93db83a3c5c0a4
(cherry picked from commit 822f5840c0f498e33829a0a00f383d9be3a7e913)
2 files changed