Add attributes.codegen.inline.externally-exported
This rule did not seem to be covered elsewhere. I'm not 100% positive
this is the best way to document this, but I think it is accurate.
This is implemented in
https://github.com/rust-lang/rust/blob/5526a2f47cd676ceeedc08cf71ae75ce2e9284ae/compiler/rustc_passes/src/check_attr.rs#L482-L497
diff --git a/src/attributes/codegen.md b/src/attributes/codegen.md
index ccc9477..e78309e 100644
--- a/src/attributes/codegen.md
+++ b/src/attributes/codegen.md
@@ -65,6 +65,9 @@
r[attributes.codegen.inline.trait]
When `inline` is applied to a function in a [trait definition], it applies only to that function when used as a default function for a trait implementation and not to all trait implementations.
+r[attributes.codegen.inline.externally-exported]
+The `inline` attribute is ignored if the function is externally exported. This may happen with the [`no_mangle`] or [`export_name`] attribute.
+
r[attributes.codegen.cold]
### The `cold` attribute
