go/gcexportdata: fix test again (fix older builds)
go/gcexportdata: fix test again (fix older builds)

This time, chose a package that's not changed across several builds.
Follow-up on https://go-review.googlesource.com/45151.

Change-Id: I0b487a45f8b12179b3aa495d852c0b7caa44c921
Reviewed-on: https://go-review.googlesource.com/45154
Run-TryBot: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>
Reviewed-by: Alan Donovan <7069e9552f9d110b0a0f326b96f22f63fb99dfc1@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

syreclabs/go-tools,golang/tools,golang/tools,syreclabs/go-tools,syreclabs/go-tools,syreclabs/go-tools,syreclabs/go-tools,golang/tools,golang/tools,golang/tools,syreclabs/go-tools