cmd/cgo/internal/testsanitizers: fix TSAN tests using setarch
Some systems don't have permissions to run setarch, for example
when running in a docker container without the --privileged flag.
This change makes the tests skip the setarch command if it fails.
Fixes #70463
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-asan-clang15
Change-Id: I02fbd423ba809f5229b8639c9abe6fd275f32558
Reviewed-on: https://go-review.googlesource.com/c/go/+/630096
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>