Make sure that our version of certain utility function implementations gets used in the firmware.

firmware/lib/utility.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.
+ *
+ * Utility functions that need to be built as part of the firmware.
+ */
+
+#include "utility.h"
+
+void* Memset(void* d, const uint8_t c, uint64_t n) {
+  uint8_t* dest = d; /* the only way to keep both cl and gcc happy */
+  while (n--) {
+    *dest++ = c;
+  }
+  return dest;
+}
+
+int SafeMemcmp(const void* s1, const void* s2, size_t n) {
+  int result = 0;
+  if (0 == n)
+    return 1;
+
+  const unsigned char* us1 = s1;
+  const unsigned char* us2 = s2;
+  /* Code snippet without data-dependent branch due to
+   * Nate Lawson (nate@root.org) of Root Labs. */
+  while (n--)
+    result |= *us1++ ^ *us2++;
+
+  return result != 0;
+}