Draft: blake3: Add C based libblake3
This updates the blake3 rust packaging to also produce libblake3-0
and libblake3-dev
which can be linked as a C library.
The motivation for this is that newer versions of the nix
package rely on libblake3.
I verified that the previously produced librust-blake3-dev
package appears to be the same, and I verified the 2 new packages for the C library with the nix package.