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

native_client_sdk/src/libraries/nacl_io/kernel_wrap_newlib.cc

Index: native_client_sdk/src/libraries/nacl_io/kernel_wrap_newlib.cc
diff --git a/native_client_sdk/src/libraries/nacl_io/kernel_wrap_newlib.cc b/native_client_sdk/src/libraries/nacl_io/kernel_wrap_newlib.cc
index be1d75937a72e0314214b6cac1b49dd00595cb0b..0809866547ba522e6b8720ddeab08f0fb86c6aa7 100644
--- a/native_client_sdk/src/libraries/nacl_io/kernel_wrap_newlib.cc
+++ b/native_client_sdk/src/libraries/nacl_io/kernel_wrap_newlib.cc
@@ -314,12 +314,6 @@ int _real_write(int fd, const void* buf, size_t count, size_t* nwrote) {
   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() {