archive/zip: if non-zero base offset fails, fall back to zero
This permits us to read files that earlier Go releases could read.
It is also compatible with other zip programs.
Change-Id: I7e2999f1073c4db5ba3f51f92681e0b149d55b3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/408734
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com> Reviewed-by: Michael Knyszek <mknyszek@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>