State 'build.rs' location explicitly
For users like me that are newer to rust, it isn't clear that the
`build.rs` file goes next to Cargo.toml rather than in `src` so it seems
sensible to indicate this clearly. It took quite a bit of googling to
figure this out.
@@ -56,8 +56,9 @@ hand and use it with LALRPOP, then check out the [lexer tutorial].)
[the next section]: 002_paren_numbers.md
[lexer tutorial]: ../lexer_tutorial/index.md
-Next we have to add `build.rs` itself. This should just look like the
-following:
+Next we have to add `build.rs` itself. For those unfamiliar with this feature, the `build.rs` file
+should be placed next to your `Cargo.toml` file and not inside the `src` folder with the rest of
+your Rust code. This should just look like the following:
```rust
extern crate lalrpop;
