message: Added dlerror() error message to log.
  This can provide more information when libneuralnetworks.so cannot be loaded successfully.
diff: @@ -146,9 +146,14 @@ const NnApi LoadNnApi() {
  void* libneuralnetworks = nullptr;
  // TODO(b/123243014): change RTLD_LOCAL? Assumes there can be multiple
  // instances of nn api RT
  - libneuralnetworks = dlopen("libneuralnetworks.so", RTLD_LAZY | RTLD_LOCAL);
  + static const char nnapi_library_name[] = "libneuralnetworks.so";
  + libneuralnetworks = dlopen(nnapi_library_name, RTLD_LAZY | RTLD_LOCAL);
  if (libneuralnetworks == nullptr) {
  - NNAPI_LOG("nnapi error: unable to open library %s", "libneuralnetworks.so");
  + const char* error = dlerror();
  + if (error) {
  + NNAPI_LOG("%s\n", error);
  + }
  + NNAPI_LOG("nnapi error: unable to open library %s", nnapi_library_name);
  }
  nnapi.nnapi_exists = libneuralnetworks != nullptr;
  