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

native_client_sdk/src/libraries/nacl_io/kernel_wrap_glibc.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 <sys/types.h>  // Include something that will define __GLIBC__.
 
 // The entire file is wrapped in this #if. We do this so this .cc file can be
 // compiled, even on a non-glibc build.
 #if defined(__native_client__) && defined(__GLIBC__)
 
@@ skipping 370 matching lines @@
 int _real_rmdir(const char* pathname) {
   CHECK_REAL(rmdir);
   return REAL(rmdir)(pathname);
 }
 
 int _real_write(int fd, const void *buf, size_t count, size_t *nwrote) {
   CHECK_REAL(write);
   return REAL(write)(fd, buf, count, nwrote);
 }
 
-uint64_t usec_since_epoch() {
-  struct timeval tv;
-  gettimeofday(&tv, NULL);
-  return tv.tv_usec + (tv.tv_sec * 1000000);
-}
-
 static bool s_wrapped = false;
 void kernel_wrap_init() {
   if (!s_wrapped) {
     assign_real_pointers();
     EXPAND_SYMBOL_LIST_OPERATION(USE_WRAP)
     s_wrapped = true;
   }
 }
 
 void kernel_wrap_uninit() {
   if (s_wrapped) {
     EXPAND_SYMBOL_LIST_OPERATION(USE_REAL)
     s_wrapped = false;
   }
 }
 
 EXTERN_C_END
 
 #endif  // defined(__native_client__) && defined(__GLIBC__)