[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

Index: native_client_sdk/src/tests/nacl_io_test/mount_html5fs_test.cc
diff --git a/native_client_sdk/src/tests/nacl_io_test/mount_html5fs_test.cc b/native_client_sdk/src/tests/nacl_io_test/mount_html5fs_test.cc
index 12f4fcfc35f6e92732f50978eb1390ccf5393137..3f1bd11b14d0db3b7c12cb22da5c4e8cc1998732 100644
--- a/native_client_sdk/src/tests/nacl_io_test/mount_html5fs_test.cc
+++ b/native_client_sdk/src/tests/nacl_io_test/mount_html5fs_test.cc
@@ -452,7 +452,7 @@ TEST_F(MountHtml5FsTest, GetDents) {
     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);
@@ -476,7 +476,7 @@ TEST_F(MountHtml5FsTest, GetDents) {
     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);