[clang] [Clang] Introduce __builtin_is_modifiable_lvalue() (PR #132524)

[via cfe-commits]

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@@ -158,6 +158,7 @@ Non-comprehensive list of changes in this release
 
 - Support parsing the `cc` operand modifier and alias it to the `c` modifier (#GH127719).
 - Added `__builtin_elementwise_exp10`.
+- Added `__builtin_is_modifiable_lvalue` to identify assignable arguments in macros.
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Sirraide wrote:

```suggestion
- Added `__builtin_is_modifiable_lvalue`.
```
I’d honestly just omit this since you could just as well use it outside of macros.

https://github.com/llvm/llvm-project/pull/132524