Fix cross-crate documentation link to objc2::topics

At least on docs.rs, the link is still broken when generating local
documentation.

Author: madsmtm

crates/header-translator/src/default_cargo.toml

@@ -20,6 +20,7 @@ workspace = true
 [package.metadata.docs.rs]
 default-target = "UNSET"
 features = ["all"]
+rustc-args = ["--cfg", "docsrs"] # Fix cross-crate link to objc2::topics
 targets = [
 ]
 

crates/objc2/src/lib.rs

@@ -211,7 +211,7 @@ pub mod runtime;
 #[cfg(test)]
 mod test_utils;
 mod top_level_traits;
-#[cfg(any(doc, doctest, test))]
+#[cfg(any(docsrs, doc, doctest, test))]
 pub mod topics;
 mod verify;