debug/gosym: in test, use temp binary name in /tmp, and clean up.

This fixes all.bash on shared machines.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5992078

src/pkg/debug/gosym/pclntab_test.go

@@ -7,14 +7,19 @@ package gosym
 import (
 	"debug/elf"
 	"fmt"
+	"io/ioutil"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"runtime"
 	"strings"
 	"testing"
 )
 
-var pclinetestBinary string
+var (
+	pclineTempDir    string
+	pclinetestBinary string
+)
 
 func dotest() bool {
 	// For now, only works on ELF platforms.
@@ -24,10 +29,18 @@ func dotest() bool {
 	if pclinetestBinary != "" {
 		return true
 	}
+	var err error
+	pclineTempDir, err = ioutil.TempDir("", "pclinetest")
+	if err != nil {
+		panic(err)
+	}
+	if strings.Contains(pclineTempDir, " ") {
+		panic("unexpected space in tempdir")
+	}
 	// This command builds pclinetest from pclinetest.asm;
 	// the resulting binary looks like it was built from pclinetest.s,
 	// but we have renamed it to keep it away from the go tool.
-	pclinetestBinary = os.TempDir() + "/pclinetest"
+	pclinetestBinary = filepath.Join(pclineTempDir, "pclinetest")
 	command := fmt.Sprintf("go tool 6a -o %s.6 pclinetest.asm && go tool 6l -E main -o %s %s.6",
 		pclinetestBinary, pclinetestBinary, pclinetestBinary)
 	cmd := exec.Command("sh", "-c", command)
@@ -170,6 +183,7 @@ func TestPCLine(t *testing.T) {
 	if !dotest() {
 		return
 	}
+	defer os.RemoveAll(pclineTempDir)
 
 	f, tab := crack(pclinetestBinary, t)
 	text := f.Section(".text")