Revert "cmd/link: skip symbol references when looking for missing symbols"

This reverts commit 8adc1e00.

Reason for revert: The test added in this commit fails on several
builders.

Fixes #36389. Re-opens #33979.

Change-Id: I31191098c36af00f7688749b3376686673b3ac68
Reviewed-on: https://go-review.googlesource.com/c/go/+/213417


Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alberto Donizetti <alb.donizetti@gmail.com>