[clang] [Clang] [NFC] Add release note about libstdc++ bug (PR #93059)

[via cfe-commits]

https://github.com/Sirraide created https://github.com/llvm/llvm-project/pull/93059

Adding a release note about this as discussed in #92439. 

(This is an NFC change, but I’m adding you as reviewers in case there is anything you want to add to this since you were involved in the discussion.)

This closes #92439.

>From b7fde11f08a324b00e8179253dd327724b40cdc9 Mon Sep 17 00:00:00 2001
From: Sirraide <aeternalmail at gmail.com>
Date: Wed, 22 May 2024 17:49:11 +0200
Subject: [PATCH] [Clang] Add release note about libstdc++ bug

---
 clang/docs/ReleaseNotes.rst | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 5a123b0b86dda..58c73fb6947ce 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -59,6 +59,18 @@ C++ Specific Potentially Breaking Changes
 - Clang now performs semantic analysis for unary operators with dependent operands
   that are known to be of non-class non-enumeration type prior to instantiation.
 
+  This change uncovered a bug in libstdc++ 14.1.0 which may cause compile failures
+  on systems using that version of libstdc++ and Clang 19, with an error that looks
+  something like this:
+
+  .. code-block:: text
+
+    <source>:4:5: error: expression is not assignable
+    4 |     ++this;
+      |     ^ ~~~~
+
+  To fix this, update libstdc++ to a newer version, such as 14.1.1 or 14.2.
+
 ABI Changes in This Version
 ---------------------------
 - Fixed Microsoft name mangling of implicitly defined variables used for thread