zstd library dependency still needed ?

[hzeller]

There is a dependency on zstd https://github.com/google/xls/blob/main/dependency_support/load_external.bzl#L62-L73

I was considering adding the additional targets in our BUILD file for zstd and upstreaming it to the BZR version https://registry.bazel.build/modules/zstd ...

However, right now it looks like it is not referenced anywhere in our BUILD files, so maybe we don't need this anymore ? Is all the zstd testing done using riegeli ?

I might be wrong though, there is a pending PR #3636 so maybe that needs that dependency.
Tagging @magancarz (author of that PR) and @proppy (reviewer?)

[magancarz]

We are using it to generate tests random data or to decompress given test case for expected values in data_generator.py added with PR #3636.