Expose C header files via DEP_ environment variable

[jschwe]

Could libz-rs-sys add a build-script to expose the C header files by adding a:

println!("cargo:include={}/include", dst.to_str().unwrap());

This is done by libz-sys https://github.com/rust-lang/libz-sys/blob/1c2c7b04f585f86d9bd203bccf631a5dc2bdabc4/build.rs#L171, and users can read the DEP_<crate_name>_<key_name> environment variable in build scripts.

[folkertdev]

For security reasons we really don't want to add a build script. The header file is provided just for convenience, the zlib header has not meaningfully changed in ~2 decades I think.

[jschwe]

Is the concern here, that the simple introduction of a build.rs script will raise flags / concerns by security tooling?
The actual content of the build.rs would just be a println!("cargo:metadata") line.

The header file is provided just for convenience, the zlib header has not meaningfully changed in ~2 decades I think.

I guess thats fair, it just seems slightly inconvenient to need to vendor the file, when previously it was made available by libz-sys.