cmd/link: move issue 43830 tests out of TestScript

These tests pass or fail depending on the exact compiler version,
which the TestScript tests don't support. Rewrite into Go.

For #43830
For #46295

Change-Id: I91b61dfe329d518e461ee56f186f0e9b42858e77
Reviewed-on: https://go-review.googlesource.com/c/go/+/324049


Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>