message: Fix `generate_doc.sh` issue
  Script genreate_docs.sh is looking for build directory existance;
  but it should actually check `build/default` directory's contents.
  After `make clean`, contents of dir `build/default` will be empty.
diff: @@ -23,7 +23,7 @@ install_prefix="$source_dir/install"
  if [ "$skip_checks" = false ]; then
  # Clean-up build & install directory
  - if [ -e $source_dir/build/ ] || [ -e $install_prefix ] ; then
  + if [ "$(ls $source_dir/build/default)" ] || [ -e $install_prefix ] ; then
  printf "Clean-up your build & install directory using below command.\nmake clean && rm -rf $install_prefix\n"
  exit 1
  fi
  