Build dependency awareness

[alexcrichton]

As issues like #1240 and #888 talk about, build scripts are not exactly trivial to write right now. We've got a fantastic system for making them easier to write via build-dependencies, but there's no current great way to discover build dependencies.

I think that we need a better strategy for promoting build dependencies, raising awareness about them, and generally discouraging "please install these 4 libs" sections of READMEs in favor of having scripts themselves take care of the necessities.

Some possible ideas:

• Add an "official" build-dependency keyword on crates.io
• Add a curated list of known build dependencies that are good for use.
• Expand documentation about build dependencies and how best to utilize them
• Have a list of "wanted build dependencies" for functionality that should be in a separate crate but currently isn't

I do think that some work is going to be need to put into writing some new build dependencies as I have a feeling we're still lacking some basic utilities. It's good track some of this though!

[kornelski]

I've searched crates.io for "automake", "autotools", "configure", "cmake" and haven't found anything that would be able to integrate with C toolchain, so help there would be great!

[pnkfelix]

cc me

[brson]

@alexcrichton Removed P-high since this is inactive.

[sanxiyn]

Update? This issue started from #888 which is basically that src/doc/build-script.md used handwavy cc crate. But #1760 changed the documentation to use actually existing gcc crate, and added example of adding build-dependencies section to Cargo.toml.

[alexcrichton]

This is still a pretty hand-wavy bug, but I don't think it's done in the sense that there's not a one-stop-shop for "how do I write this build script" or things like "best build script practices" yet.