tg.sleep()
	restore := addVar(sys, 0)
	restore()
	tg.wantNotStale("p1", "", "./testgo list claims p1 is stale, incorrectly, after updating mtime of runtime/internal/sys/sys.go")

	// But changing content of any file should have an effect.
	// Previously zversion.go was the only one that mattered;
	// now they all matter, so keep using sys.go.
	restore = addVar(sys, 1)
	defer restore()