rustdoc drops `#[no_mangle]` and `#[link_section]` from inlined cross-crate re-exported fns & statics

[fmease]

Reproduction:

• rustc a.rs --crate-type lib --edition 2024 a.rs where a.rs:

  #[unsafe(no_mangle)]
  pub fn f0() {}
  
  #[unsafe(link_section = ".here")]
  pub fn f1() {}
  
  #[unsafe(no_mangle)]
  pub static S0: () = ();
  
  #[unsafe(link_section = ".there")]
  pub static S1: () = ();

• rustdoc b.rs --edition 2024 -L. --extern a where b.rs:

  pub use a::*;

Behavior:

• On 1.88.0 (current stable), rustdoc doesn't render any of these attributes
• On 1.89.0-beta.5 (current beta), rustdoc renders the #[no_mangle]s but not the #[link_section]s
• On 1.90.0-nightly (3014e79 2025-07-15) (current master), rustdoc doesn't render any of these attributes yet again

The attributes #[repr], #[non_exhaustive] & #[export_name] are unaffected (i.e., the remaining allowlisted non-doc attrs).

[fmease]

Unfortunately, I don't have the time to dig into this rn. Note that PR #143083 addressed local re-exports, not cross-crate ones.

cc @jdonszelmann @JonathanBrouwer (no obligations :^D)

[fmease]

(We should definitely test this scenario for all of these attributes in the pre-existing tests/rustdoc/inline_cross/attributes.rs which only exercises #[non_exhaustive] rn (a regression test in and of itself) this flip-flopping is ridiculous xD)

[JonathanBrouwer]

This is probably related to the fact that these attributes are "No" here: https://github.com/rust-lang/rust/blob/master/compiler%2Frustc_attr_data_structures%2Fsrc%2Fencode_cross_crate.rs

@rustbot claim
Might take me a few days to find time but I'll dive into it

[bjorn3]

They can be recovered using the codegen_fn_attrs query.