Add `libc++-dev` package to linux environment

[nicoburns]

We're using libc++ (clang's C++ standard library) instead of libstdc++ for yoga-rs because using libstdc++ / using whatever is set as default was causing bindgen to generate code that wouldn't compile.

However, this dependency is missing in the build environment which is causing building docs for docs.rs to fail (https://github.com/rust-lang/docs.rs/issues/2017)

[nicoburns]

https://bugs.launchpad.net/ubuntu/+source/llvm-toolchain-14/+bug/1989124