Rely on an external package for portability questions about the libc

[agagniere]

Several C libraries packaged with Zig build (LibreSSL, libpq) have to answer the same questions about wether the target's libc has a given function / header.
So I'm centralizing the logic in a single package, that takes versions into account, and generates what it can from the Zig toolchain.

The main benefit for a package like curl is a decrease in complexity and maintenance burden.

I already migrated libpq, and will do LibreSSL next (even though it is there that I started initially)

[Techatrix]

This libc-query idea seems very interesting. However, I'm already relying on my own tool that automatically extracts config headers from the upstream build system (cmake in this case) and converts them into b.addConfigHeader which I'm partially using for this curl package. I don't think that relying on libc-query would ultimately decrease the maintenance burden on this project for me.

If this package gains adoption within allyourcodebase and continues to be well maintained over time, I may reconsider.