Add helper functions and files for gpt tests.

src/platform/vboot_reference/common/utility_stub.c

 /* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  * Stub implementations of utility functions which call their linux-specific
  * equivalents.
  */
 
 #include "utility.h"
 
@@ skipping 24 matching lines @@
     /* Fatal Error. We must abort. */
     abort();
   }
   return p;
 }
 
 void Free(void* ptr) {
   free(ptr);
 }
 
+int Memcmp(const void* src1, const void* src2, size_t n) {
+  return memcmp(src1, src2, n);
+}
+
 void* Memcpy(void* dest, const void* src, size_t n) {
   return memcpy(dest, src, n);
 }
 
 void* Memset(void* dest, const uint8_t c, size_t n) {
   while (n--) {
     *((uint8_t*)dest++) = c;
   }
   return dest;
 }
@@ skipping 30 matching lines @@
     return NULL;
   if (len > state->remaining_len) {
     state->overrun = 1;
     return NULL;
   }
   Memcpy(state->remaining_buf, src, len);
   state->remaining_buf += len;
   state->remaining_len -= len;
   return src;
 }