loongson/pypi: links for approxmath

loongson/mirror approxmath-2.0.0.tar.gz
loongson/mirror approxmath-2.0.0-py3.9-macosx-10.15-x86_64.egg
loongson/mirror approxmath-1.0.1.tar.gz
loongson/mirror approxmath-1.0.0.tar.gz