[mojo-edk] Make the Mojo EDK compile under NaCl.

mojo/edk/embedder/platform_channel_utils_posix.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/edk/embedder/platform_channel_utils_posix.h"
 
 #include <stddef.h>
 #include <sys/socket.h>
+#if !defined(OS_NACL)
 #include <sys/uio.h>
+#endif
 #include <unistd.h>
 
 #include "base/logging.h"
 #include "base/posix/eintr_wrapper.h"
 #include "build/build_config.h"
 
 #if !defined(SO_PEEK_OFF)
 #define SO_PEEK_OFF 42
 #endif
 
@@ skipping 164 matching lines @@
         DCHECK(platform_handles->back().is_valid());
       }
     }
   }
 
   return result;
 }
 
 }  // namespace edk
 }  // namespace mojo