all: use t.TempDir in tests

This removes all usage of ioutil.TempDir in tests (and a few cases of
os.TempDir as well, while we're at it), which simplifies test cleanup a
lot.

Compile tested (go test -c) for most platforms (except zos).

Change-Id: I9178f5ec615c0a6cfef36e8de78c6b72e055b7cb
Reviewed-on: https://go-review.googlesource.com/c/sys/+/526297
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: qiulaidongfeng <2645477756@qq.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>

unix/dirent_test.go

@@ -11,7 +11,6 @@ import (
 	"bytes"
 	"fmt"
 	"io/ioutil"
-	"os"
 	"path/filepath"
 	"runtime"
 	"sort"
@@ -29,16 +28,12 @@ func TestDirent(t *testing.T) {
 		filenameMinSize = 11
 	)
 
-	d, err := ioutil.TempDir("", "dirent-test")
-	if err != nil {
-		t.Fatalf("tempdir: %v", err)
-	}
-	defer os.RemoveAll(d)
+	d := t.TempDir()
 	t.Logf("tmpdir: %s", d)
 
 	for i, c := range []byte("0123456789") {
 		name := string(bytes.Repeat([]byte{c}, filenameMinSize+i))
-		err = ioutil.WriteFile(filepath.Join(d, name), nil, 0644)
+		err := ioutil.WriteFile(filepath.Join(d, name), nil, 0644)
 		if err != nil {
 			t.Fatalf("writefile: %v", err)
 		}
@@ -98,18 +93,14 @@ func TestDirentRepeat(t *testing.T) {
 	}
 
 	// Make a directory containing N files
-	d, err := ioutil.TempDir("", "direntRepeat-test")
-	if err != nil {
-		t.Fatalf("tempdir: %v", err)
-	}
-	defer os.RemoveAll(d)
+	d := t.TempDir()
 
 	var files []string
 	for i := 0; i < N; i++ {
 		files = append(files, fmt.Sprintf("file%d", i))
 	}
 	for _, file := range files {
-		err = ioutil.WriteFile(filepath.Join(d, file), []byte("contents"), 0644)
+		err := ioutil.WriteFile(filepath.Join(d, file), []byte("contents"), 0644)
 		if err != nil {
 			t.Fatalf("writefile: %v", err)
 		}