message: Intercept POPLAR_ENGINE_OPTIONS for generating the hash
  Summary: POPLAR_ENGINE_OPTIONS affects the program being generated.
  Reviewers: #tensorflow, hakons
diff: @@ -1273,6 +1273,12 @@ Status PoplarExecutor::ConfigurePoplarDevice(const IpuOptions& cfg) {
  // Get environment PoplarXlaFlags hash
  target_hash.push_back(PoplarXlaFlags::Get().hlo_hash);
  + // TODO(T12447) - use a hash returned by Poplar.
  + char* env_engine_options = getenv("POPLAR_ENGINE_OPTIONS");
  + if (env_engine_options) {
  + target_hash.push_back(std::hash<string>()(std::string(env_engine_options)));
  + }
  +
  poplar_device_hash_ = CombinedHash(target_hash);
  return Status::OK();
  