runtime: fix TestDeferWithRepeatedRepanics and TestIssue37688 to be less chatty
Converted some Println() statements (used to make sure that certain variables were
kept alive and not optimized out) to assignments into global variables, so the
tests don't produce extraneous output when there is a failure.
Fixes #38594
Change-Id: I7eb41bb02b2b1e78afd7849676b5c85bc11c759c
Reviewed-on: https://go-review.googlesource.com/c/go/+/229538
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>