Rollup merge of #119590 - ChrisDenton:cfg-target-abi, r=Nilstrieb

Stabilize `cfg_target_abi`

This stabilizes the `cfg` option called `target_abi`:

```rust
#[cfg(target_abi = "eabihf")]
```

Tracking issue: #80970

fixes #78791
resolves #80970

Author: matthiaskrgr