Add section for non-Cargo based build systems + fix typos

Author: Urgau

posts/2024-04-29-check-cfg.md

@@ -97,19 +97,23 @@ More details can be found on the [`rustc` book](https://doc.rust-lang.org/nightl
 
 The feature is **always on** and _cannot_ be disabled from Cargo, but like any other lints it can be controlled: `#![allow(unexpected_cfgs)]`.
 
-### How does it interact with the `RUSTFLAGS` env ?
+### Does the lint affect dependencies?
+
+No, the lint only affects local packages; only those will report the lint.
+
+### How does it interact with the `RUSTFLAGS` env?
 
 You should be able to use the `RUSTFLAGS` environment variable like it was before.
 *Currently `--cfg` arguments are not checked, only usage in code are.*
 
 This means that doing `RUSTFLAGS="--cfg tokio_unstable" cargo check` will not report any warnings, unless `tokio_unstable` is used within your local crates, in which case crate author will need to make sure that that custom cfg is expected with `cargo::rustc-check-cfg` in the `build.rs` of that crate.
 
-### How to expect custom cfgs without a `build.rs` ?
+### How to expect custom cfgs without a `build.rs`?
 
-There is not **currently no way** to expect a custom cfg other than with `cargo::rustc-check-cfg` in a `build.rs`.
+There is **currently no way** to expect a custom cfg other than with `cargo::rustc-check-cfg` in a `build.rs`.
 
 Crate authors that don't want to use a `build.rs` are encouraged to use Cargo features instead.
- 
-### Does the lint affect dependencies?
 
-No, the lint only affects local packages; only those will report the lint.
+### How does it interact with other build systems?
+
+Non-Cargo based build systems are not affected by the lint by default. Build system authors that wish to have the same functionality should look at the `rustc` documentation for the [`--check-cfg`](https://doc.rust-lang.org/nightly/rustc/check-cfg.html) flag for a detailed explanation of how to achieve the same functionality.