I got this stuff by cloning https://github.com/cds-astro/cds-healpix-rust.git
cd-in into libpython, running

RUSTFLAGS='-C target-cpu=native' cargo build --release

and copying target/release/libcdshealpix_ffi.so and python/healpix.py
to here.  It's used to create the MOCs while the C++ library sucks
when making polygons.