libz-sys and libnghttp2-sys are only used so that the corresponding C libraries are linked against the bundled static libcurl (which is not built).

We probably need to put proper patch for upstream so that we don't patch code at all.

The problem is that whether the bundled curl is used is decided during build time after features (and dependencies) have been set.

If we convinced upstream to not automagically build curl if they can't find the system one, the problem remains: Cargo optional dependencies are only of the form

• single-feature -> feature
• single-feature -> package
• single-feature -> package AND package-with-feature

What we want is something like
static-curl AND ssl -> openssl-sys

which cannot be expressed at the moment.

Apparently it is possible, as shown in https://github.com/rustgd/collision-rs/blob/master/Cargo.toml

I'll test that and try to upstream it.

That didn't work. Features are not set when evaulating target.'cfg(...)'.dependencies.