cmd/link/internal/ld: clean tmpdir obj timestamps
This patch changes the Go linker to "clean" (reset to Unix epoch) the
timestamps on object files copied to the tmpdir that is presented to
the external linker or archive tool. The intent is to improve build
reproducibility on Darwin, where later versions of xcode seem to want
to incorporate object file timestamps into the hash used for the final
build ID (which precludes the possibility of having reproducible Go
builds). Credit for this idea goes to Cherry (see
https://github.com/golang/go/issues/64947#issuecomment-
1887667189).
Updates #64947.
Change-Id: I2eb7dddff538e247122b04fdcf8a57c923f61201
Reviewed-on: https://go-review.googlesource.com/c/go/+/585355
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>