Rollup merge of #111096 - AngelicosPhosphoros:overflow_checks_issue_91130, r=petrochenkov

Add support for `cfg(overflow_checks)`

This PR adds support for detecting if overflow checks are enabled in similar fashion as `debug_assertions` are detected. Possible use-case of this, for example, if we want to use checked integer casts in builds with overflow checks, e.g.

```rust
pub fn cast(val: usize)->u16 {
    if cfg!(overflow_checks) {
        val.try_into().unwrap()
    }
    else{
        vas as _
    }
}
```

Resolves #91130.

0 files changed, 0 insertions, 0 deletions