loongson/pypi: links for gast

INFO: Because this project isn't in the mirror_whitelist, no releases from root/pypi are included.

loongson/pypi gast-0.5.3.tar.gz
loongson/pypi gast-0.5.3-py3-none-any.whl
loongson/pypi gast-0.4.0-py3-none-any.whl
loongson/pypi gast-0.3.3-py3-none-any.whl
loongson/pypi gast-0.2.2-py3-none-any.whl