Attempt 2 to fix build

runtime/platform/json.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/json.h"
 
 #include "platform/assert.h"
 #include "platform/globals.h"
 #include "platform/utils.h"
 #include "vm/os.h"
 
 namespace dart {
 
+#ifndef va_copy
+#define va_copy(dst, src) (memmove(&(dst), &(src), sizeof(dst)))
+#endif  /* va_copy */
+
 
 JSONScanner::JSONScanner(const char* json_text) {
   SetText(json_text);
 }
 
 
 void JSONScanner::SetText(const char* json_text) {
   current_pos_ = json_text;
   token_start_ = json_text;
   token_length_ = 0;
@@ skipping 361 matching lines @@
 
 void TextBuffer::GrowBuffer(intptr_t len) {
   intptr_t new_size = buf_size_ + len;
   char* new_buf = reinterpret_cast<char*>(realloc(buf_, new_size));
   ASSERT(new_buf != NULL);
   buf_ = new_buf;
   buf_size_ = new_size;
 }
 
 }  // namespace dart