[dev.link] cmd/link, cmd/oldlink: detect object file format mismatch

When using the new(old) linker but an old(new) object file is
found, give a better error message.

Change-Id: I94786f1a4b527c15c4f5b00457eab60d215a72a0
Reviewed-on: https://go-review.googlesource.com/c/go/+/225457


Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>