protocol: generate cfg docs with nightly

Cargo.lock

@@ -717,6 +717,7 @@ dependencies = [
 name = "xash3d-protocol"
 version = "0.2.0"
 dependencies = [
+ "autocfg",
  "bitflags 2.5.0",
  "log",
 ]

protocol/Cargo.toml

@@ -20,3 +20,6 @@ net = []
 [dependencies]
 log = "0.4.18"
 bitflags = "2.4"
+
+[build-dependencies]
+autocfg = "1"

protocol/build.rs

@@ -0,0 +1,7 @@
+fn main() {
+    let ac = autocfg::new();
+    println!("cargo:rustc-check-cfg=cfg(has_doc_auto_cfg)");
+    if ac.probe_raw("#![feature(doc_auto_cfg)]").is_ok() {
+        println!("cargo:rustc-cfg=has_doc_auto_cfg");
+    }
+}

protocol/src/lib.rs

@@ -7,6 +7,7 @@
 //! Xash3D protocol between clients, servers and masters.
 
 #![cfg_attr(all(not(feature = "std"), not(test)), no_std)]
+#![cfg_attr(all(doc, has_doc_auto_cfg), feature(doc_auto_cfg))]
 
 #[cfg(feature = "alloc")]
 extern crate alloc;