Pass the value of project.links into the build script

[mzabaluev]

It would be nice if the project's links value was available to the build script.
Then build helpers like pkg-config could read that, so that build.rs could be a drop-in file suitable for all -sys projects where the library provides a pkg-config file with the same name.

[mzabaluev]

Cc @alexcrichton

[alexcrichton]

Sounds like a good idea to me! Passing something like LIB or some other environment variable to the build script should work ok.

[sbeckeriv]

I did it backwards in my pull request. I was setting the links based on a variable. I am told I need to set the environment variable based on the links value. I am looking into setting the environment variable now. It looks like the standard lib https://doc.rust-lang.org/std/env/fn.set_var.html only sets the variable for the current running process. Which matches up with what I am seeing building /~https://github.com/PistonDevelopers/freetype-sys

Also I noticed pistion build parses 3 mainifest files but the last links is different. Im guessing you would only care about the first parsed.
/Users/becker/trash/cargo-becker/target/debug/cargo build setting RUST_LIB freetype setting RUST_LIB freetype setting RUST_LIB z

Let me know if there is a known way to leak out environment variable changes.

[alexcrichton]

Ah yeah you'll probably want to call .env on the relevant Command builder where we run the build script, that'll set the environment variable for only that process

[sbeckeriv]

I am understanding better. The value needs to be passed to the internal build command system. I need to read up on this and how it works! Thanks