message: Collect cpu time
  Summary: As title.
diff: #include <boost/thread/thread.hpp>
  #include <cinttypes>
  #include <cstring>
  +#include <ctime>
  #include <fstream>
  #include <iostream>
  #include <memory>
  @@ -677,13 +678,18 @@ Json::Value get_detailed_stats(const std::vector<dex_stats_t>& dexes_stats) {
  return dexes;
  }
  -Json::Value get_times() {
  +Json::Value get_times(double cpu_time_s) {
  Json::Value list(Json::arrayValue);
  for (const auto& t : Timer::get_times()) {
  Json::Value element;
  element[t.first] = std::round(t.second * 10) / 10.0;
  list.append(element);
  }
  + {
  + Json::Value cpu_element;
  + cpu_element["cpu_time"] = std::round(cpu_time_s * 10) / 10.0;
  + list.append(cpu_element);
  + }
  return list;
  }
  @@ -1196,6 +1202,7 @@ int main(int argc, char* argv[]) {
  std::string stats_output_path;
  Json::Value stats;
  + double cpu_time_s;
  {
  Timer redex_all_main_timer("redex-all main()");
  @@ -1280,9 +1287,10 @@ int main(int argc, char* argv[]) {
  Timer t("Freeing global memory");
  delete g_redex;
  }
  + cpu_time_s = ((double)std::clock()) / CLOCKS_PER_SEC;
  }
  // now that all the timers are done running, we can collect the data
  - stats["output_stats"]["time_stats"] = get_times();
  + stats["output_stats"]["time_stats"] = get_times(cpu_time_s);
  auto vm_stats = get_mem_stats();
  stats["output_stats"]["mem_stats"]["vm_peak"] =
  