[dev.link] cmd/oldlink: update with recent changes

Update the old linker to bring in recent changes made on the
master branch: CL 225397 and CL 220917.

This brings cmd/oldlink to be in sync with commit
aa4d92b8.

Change-Id: Ic386736fa30944dcb71c57096915381d3e6be82c
Reviewed-on: https://go-review.googlesource.com/c/go/+/227028


Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>