runtime: Use doas -n in TestSUID on OpenBSD
This prevents a hang at a su password prompt when running this test on
OpenBSD.
Fixes #60690.
Change-Id: I62d27aa63f225f8247c324b87b5e688319061f4f
GitHub-Last-Rev:
217813a4d57a97954449d13c24a465aa0af41da3
GitHub-Pull-Request: golang/go#60742
Reviewed-on: https://go-review.googlesource.com/c/go/+/502575
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>