cmd/link: fix TestLargeText

This test is not run in short mode so it was getting
failures that didn't happen with default testing. See
the issue for details on the failures.

Fixes #45406

Change-Id: I51d97cc4c910fe3ba2bc0a12742023a57d101f44
Reviewed-on: https://go-review.googlesource.com/c/go/+/308935


Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Paul Murphy <murp@ibm.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Trust: Lynn Boger <laboger@linux.vnet.ibm.com>