removing older C libraries

[clux]

Some of the C libraries in here are potentially less necessary down the line as rust alternatives gain complete majority and stability.

Only two candidates for removal

curl

As far as I can there are very few uses of curl variants these days (it was more common pre-hyper dominance), but the curl crate still has plenty of downloads.

zlib

The flate2 crate can possibly replace zlib as it bundles miniz.c as the default implementation.
But, don't think it works with pq, and the openssl build probably also benefits from it (it might disable gzip support otherwise).

Status

2022: This is mostly a tracking issue for me. No immediate action is planned here this year. If you use these libraries and would like them to stay, or otherwise have input on this, please leave a comment.

EDIT: 2025. it's 3 years later, and these libraries are no more useful now. curl has been removed. zlib might be removed if stuff builds fine without it.

[clux]

In the latest version curl has been removed. Combination of laziness + brokenness + not seeing it being very useful anymore. Think it's better to keep the image a little on the lighter side to cater to common use cases rather than the kitchen sink when the CI here is taking 1 hour for ARM. Plus, should make room for aws lc crypto #141

See #151 for details.