Determinism for layers

[rainersigwald]

The OCI specs say that layers should preserve timestamps, but I expect to (optionally?) violate that, because we will want to produce bit-for-bit identical output given identical repo builds, just as the Roslyn compiler does. That will require using tar APIs to set metadata on files individually to some known value.

[stan-sz]

Would this enforce <Deterministic>true</Deterministic>?

[baronfel]

This issue should be the priority amongst the Area: Incrementality issues because it directly relates to customer COGS.