include stdlib.h when using calloc

src/base/file-utils.cc

 // Copyright 2016 the V8 project 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 "src/base/file-utils.h"
 
+#include <stdlib.h>
 #include <string.h>
 
 #include "src/base/platform/platform.h"
 
 namespace v8 {
 namespace internal {
 
 char* RelativePath(char** buffer, const char* exec_path, const char* name) {
   DCHECK(exec_path);
   int path_separator = static_cast<int>(strlen(exec_path)) - 1;
   while (path_separator >= 0 &&
          !base::OS::isDirectorySeparator(exec_path[path_separator])) {
     path_separator--;
   }
   if (path_separator >= 0) {
     int name_length = static_cast<int>(strlen(name));
     *buffer =
         reinterpret_cast<char*>(calloc(path_separator + name_length + 2, 1));
     *buffer[0] = '\0';
     strncat(*buffer, exec_path, path_separator + 1);
     strncat(*buffer, name, name_length);
   } else {
     *buffer = strdup(name);
   }
   return *buffer;
 }
 
 }  // namespace internal
 }  // namespace v8