metadeps lets you write `pkg-config` dependencies in `Cargo.toml` metadata,
rather than programmatically in `build.rs`. This makes those dependencies
declarative, so other tools can read them as well.
# Usage
In your `Cargo.toml`, add the following to your `[build-dependencies]`:
```toml
metadeps = "1.1"
```
Then, to declare a dependency on `testlib >= 1.2`, and a conditional dependency
on `testdata >= 4.5`, add the following section:
```toml
[package.metadata.pkg-config]
testlib = "1.2"
testdata = { version = "4.5", feature = "use-testdata" }
```
In your `build.rs`, add:
```rust
extern crate metadeps;
fn main() {
metadeps::probe().unwrap();
}
```