`#![feature(intra_doc_pointers)]` checks the active crate for a feature gate, not the original

[jyn514]

This breaks e.g. serde: https://rust-lang.zulipchat.com/#narrow/stream/247081-t-compiler.2Fperformance/topic/serde.20doc.20runs.20broken

I tried this code:

pub use std::ptr::Pointee;

I expected to see this happen: No error occurs, because re-exporting items of the standard library should never break your crate.

Instead, this happened:

error[E0658]: linking to associated items of raw pointers is experimental
  --> /home/collector/rustc-perf/cache/0148b971c921a0831fbf3357e5936eec724e3566/lib/rustlib/src/rust/library/core/src/ptr/metadata.rs:51:23
   |
51 | /// [`to_raw_parts`]: *const::to_raw_parts
   |                       ^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #80896 <https://github.com/rust-lang/rust/issues/80896> for more information
   = help: add `#![feature(intra_doc_pointers)]` to the crate attributes to enable
   = note: rustdoc does not allow disambiguating between `*const` and `*mut`, and pointers are unstable until it does

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Version: 386d02a

[jyn514]

As a workaround, we can remove the fancy link from Pointee until this is fixed.