archive/zip: skip large concurrent tests in race mode

We recently added these large zip64 tests. They're slow-ish already,
but fast enough in non-race mode with t.Parallel. But in race mode,
the concurrency makes them much slower than the normal
non-race-to-race multiplier.

They're taking so long now that it's causing test failures when it
sometimes is over the test timeout threshold.

Change-Id: I02f4ceaa9d6cab826708eb3860f47a57b05bdfee
Reviewed-on: https://go-review.googlesource.com/33423
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/archive/zip/zip_test.go

@@ -11,6 +11,7 @@ import (
 	"errors"
 	"fmt"
 	"hash"
+	"internal/race"
 	"internal/testenv"
 	"io"
 	"io/ioutil"
@@ -296,6 +297,9 @@ func TestZip64EdgeCase(t *testing.T) {
 // Tests that we generate a zip64 file if the the directory at offset
 // 0xFFFFFFFF, but not before.
 func TestZip64DirectoryOffset(t *testing.T) {
+	if testing.Short() && race.Enabled {
+		t.Skip("skipping in short mode")
+	}
 	t.Parallel()
 	const filename = "huge.txt"
 	gen := func(wantOff uint64) func(*Writer) {
@@ -338,6 +342,9 @@ func TestZip64DirectoryOffset(t *testing.T) {
 
 // At 16k records, we need to generate a zip64 file.
 func TestZip64ManyRecords(t *testing.T) {
+	if testing.Short() && race.Enabled {
+		t.Skip("skipping in short mode")
+	}
 	t.Parallel()
 	gen := func(numRec int) func(*Writer) {
 		return func(w *Writer) {