loongson/mirror: links for py-arrow-lang

loongson/mirror py-arrow-lang-2020.6.18.tar.gz
loongson/mirror py_arrow_lang-2020.6.18-py3-none-any.whl
loongson/mirror py-arrow-lang-2020.6.17.tar.gz
loongson/mirror py_arrow_lang-2020.6.17-py3-none-any.whl