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

native_client_sdk/src/tests/nacl_io_test/mount_html5fs_test.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 <errno.h>
 #include <fcntl.h>
 
 #include <set>
 #include <string>
 
@@ skipping 434 matching lines @@
   memset(&dirents[0], 0, sizeof(dirents));
   EXPECT_EQ(
       0, root->GetDents(0, &dirents[0], sizeof(dirent) * 3 + 2, &bytes_read));
 
   {
     size_t num_dirents = bytes_read / sizeof(dirent);
     EXPECT_EQ(3, num_dirents);
     EXPECT_EQ(sizeof(dirent) * num_dirents, bytes_read);
 
     std::multiset<std::string> dirnames;
-    for (int i = 0; i < num_dirents; ++i) {
+    for (size_t i = 0; i < num_dirents; ++i) {
       EXPECT_EQ(sizeof(dirent), dirents[i].d_off);
       EXPECT_EQ(sizeof(dirent), dirents[i].d_reclen);
       dirnames.insert(dirents[i].d_name);
     }
 
     EXPECT_EQ(1, dirnames.count("file"));
     EXPECT_EQ(1, dirnames.count("."));
     EXPECT_EQ(1, dirnames.count(".."));
   }
 
   // Add another file...
   ASSERT_EQ(0, mnt->Open(Path("/file2"), O_CREAT, &node));
 
   // Read the root directory again.
   memset(&dirents[0], 0, sizeof(dirents));
   EXPECT_EQ(0, root->GetDents(0, &dirents[0], sizeof(dirents), &bytes_read));
 
   {
     size_t num_dirents = bytes_read / sizeof(dirent);
     EXPECT_EQ(4, num_dirents);
     EXPECT_EQ(sizeof(dirent) * num_dirents, bytes_read);
 
     std::multiset<std::string> dirnames;
-    for (int i = 0; i < num_dirents; ++i) {
+    for (size_t i = 0; i < num_dirents; ++i) {
       EXPECT_EQ(sizeof(dirent), dirents[i].d_off);
       EXPECT_EQ(sizeof(dirent), dirents[i].d_reclen);
       dirnames.insert(dirents[i].d_name);
     }
 
     EXPECT_EQ(1, dirnames.count("file"));
     EXPECT_EQ(1, dirnames.count("file2"));
     EXPECT_EQ(1, dirnames.count("."));
     EXPECT_EQ(1, dirnames.count(".."));
   }
 }