all: merge NaCl branch (part 1)

src/cmd/go/build.go

 // Copyright 2011 The Go Authors.  All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 package main
 
 import (
         "bufio"
         "bytes"
         "container/heap"
@@ skipping 186 matching lines @@
                 ext = dotExt[1:]
         }
         return
 }
 
 type stringsFlag []string
 
 func (v *stringsFlag) Set(s string) error {
         var err error
         *v, err = splitQuotedFields(s)
+        if *v == nil {
+                *v = []string{}
+        }
         return err
 }
 
 func splitQuotedFields(s string) ([]string, error) {
         // Split fields allowing '' or "" around elements.
         // Quotes further inside the string do not count.
         var f []string
         for len(s) > 0 {
                 for len(s) > 0 && isSpaceByte(s[0]) {
                         s = s[1:]
@@ skipping 2294 matching lines @@
 func defaultSuffix() string {
         switch runtime.GOOS {
         case "windows":
                 return ".bat"
         case "plan9":
                 return ".rc"
         default:
                 return ".bash"
         }
 }