[NaCl SDK] Enable linux host build for nacl_io and nacl_io_tests.

native_client_sdk/src/libraries/nacl_io/mount_node_mem.cc

 // Copyright (c) 2012 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 "nacl_io/mount_node_mem.h"
 
 #include <errno.h>
 #include <string.h>
 
 #include <algorithm>
@@ skipping 43 matching lines @@
 Error MountNodeMem::Write(const HandleAttr& attr,
                           const void* buf,
                           size_t count,
                           int* out_bytes) {
   *out_bytes = 0;
   AUTO_LOCK(node_lock_);
 
   if (count == 0)
     return 0;
 
-  if (count + attr.offs > stat_.st_size) {
+  if (count + attr.offs > static_cast<size_t>(stat_.st_size)) {
     Resize(count + attr.offs);
     count = stat_.st_size - attr.offs;
   }
 
   memcpy(&data_[attr.offs], buf, count);
   *out_bytes = static_cast<int>(count);
   return 0;
 }
 
 Error MountNodeMem::FTruncate(off_t new_size) {
   AUTO_LOCK(node_lock_);
   Resize(new_size);
   return 0;
 }
 
 void MountNodeMem::Resize(off_t new_size) {
-  if (new_size > data_.capacity()) {
+  if (new_size > static_cast<off_t>(data_.capacity())) {
     // While the node size is small, grow exponentially. When it starts to get
     // larger, grow linearly.
     size_t extra = std::min<size_t>(new_size, kMaxResizeIncrement);
     data_.reserve(new_size + extra);
   } else if (new_size < stat_.st_size) {
     // Shrink to fit. std::vector usually doesn't reduce allocation size, so
     // use the swap trick.
     std::vector<char>(data_).swap(data_);
   }
   data_.resize(new_size);
   stat_.st_size = new_size;
 }
 
 }  // namespace nacl_io