cmd/go: fix build

Change-Id: I2cd58a665d9df26583128c633c443325dcc3f288
Reviewed-on: https://go-review.googlesource.com/11131Reviewed-by: Minux Ma <minux@golang.org>

src/cmd/go/note_test.go

@@ -5,10 +5,10 @@
 package main
 
 import (
+	"internal/testenv"
 	"io/ioutil"
 	"os"
 	"os/exec"
-	"runtime"
 	"testing"
 )