[clang] [clang] Implement `__is_layout_compatible` (PR #81506)

[via cfe-commits]

================
@@ -90,6 +90,12 @@ C++20 Feature Support
   behavior can use the flag '-Xclang -fno-skip-odr-check-in-gmf'.
   (`#79240 <https://github.com/llvm/llvm-project/issues/79240>`_).
 
+- Implemented `__is_layout_compatible` intrinsic, which backs up
+  `P0466R5: Layout-compatibility and Pointer-interconvertibility Traits <https://wg21.link/P0466R5>`_.
+  `CWG1719: Layout compatibility and cv-qualification revisited  <https://cplusplus.github.io/CWG/issues/1719.html>`_
+  and `CWG2759: [[no_unique_address] and common initial sequence <https://cplusplus.github.io/CWG/issues/2759.html>`_
+  are not yet implemented.
+
----------------
cor3ntin wrote:

```suggestion
- Implemented the `__is_layout_compatible` intrinsic to support
  `P0466R5: Layout-compatibility and Pointer-interconvertibility Traits <https://wg21.link/P0466R5>`_.
  Note: `CWG1719: Layout compatibility and cv-qualification revisited  <https://cplusplus.github.io/CWG/issues/1719.html>`_
  and `CWG2759: [[no_unique_address] and common initial sequence <https://cplusplus.github.io/CWG/issues/2759.html>`_
  are not yet implemented.

```

https://github.com/llvm/llvm-project/pull/81506