message: Fix esp32 ci build
  `readable_run export ` do not export variable for the environment
  Used direct export instead.
diff: @@ -28,8 +28,9 @@ source tensorflow/lite/micro/tools/ci_build/helper_functions.sh
  TARGET=esp
  # setup esp-idf and toolchains
  +echo "Checking out esp-idf..."
  readable_run git clone --recursive --single-branch --branch release/v4.2 https://github.com/espressif/esp-idf.git
  -readable_run export IDF_PATH="${ROOT_DIR}"/esp-idf
  +export IDF_PATH="${ROOT_DIR}"/esp-idf
  cd $IDF_PATH
  readable_run ./install.sh
  readable_run . ./export.sh
  