[lld] [LLD] [COFF] Pick timestamps from the SOURCE_DATE_EPOCH variable (PR #81326)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

> Does this deserve an update of the release notes for 18.0?

Good point - yeah I think it does; I can make a separate PR to update the notes on the branch.

https://github.com/llvm/llvm-project/pull/81326