testing/river: upgrade to 0.3.2

This is probably(?) the first package to use the new Zig 0.3.2 package manager. Thereby rasing the questions of how we want to deal with this package manager in aports. The Zig package manager tracks dependencies in the build.zig.zon as a pair of source tarballs and checksums. The zig build command will automatically fetch these tarballs and verify there checksum. Hence, similar to Go and Rust. I think it would be fine to just have Zig fetch these dependencies for us.

I experimented a bit with alternatives to that to ensure a build without options=net. One thing that we could do shortterm is tracking these dependencies in $source and having prepare() prepare the dependency store for us. This probably doesn't scale to well for many dependencies. A proper solution would be packing Zig dependencies, see: https://github.com/chimera-linux/cports/pull/1395

See also: https://codeberg.org/river/river/src/branch/master/PACKAGING.md#zig-package-manager

Maybe we should just have zig build fetch the dependencies for us for now? As we do with Go, Rust and Haskell packages and then later migrate to packaging Zig dependencies as individual packages?

@selfisekai what do you think?