cmd/cgo/internal/testsanitizers: make the libfuzzer tests all short
CL 589295 only made one of the two tests short, because the other one
seemed to be passing consistently in short mode. On the builders, it
seems to still fail maybe 30% of the time by taking too long. Disable
these tests in short mode.
For #67698.
Change-Id: I9fd047f834f7493b608dd1fee5b9b6dfabbea03d
Cq-Include-Trybots: luci.golang.try:gotip-linux-amd64-clang15,gotip-linux-386-clang15
Reviewed-on: https://go-review.googlesource.com/c/go/+/589495
Auto-Submit: Michael Knyszek <mknyszek@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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