[clang] [clang] Lower _BitInt(129+) to a different type in LLVM IR (PR #91364)

[John McCall via cfe-commits]

================
@@ -610,8 +610,26 @@ bool ConstStructBuilder::AppendBytes(CharUnits FieldOffsetInChars,
 }
 
 bool ConstStructBuilder::AppendBitField(
-    const FieldDecl *Field, uint64_t FieldOffset, llvm::ConstantInt *CI,
+    const FieldDecl *Field, uint64_t FieldOffset, llvm::Constant *C,
     bool AllowOverwrite) {
+
+  llvm::ConstantInt *CI = nullptr;
----------------
rjmccall wrote:

```suggestion
  llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(C);
```

https://github.com/llvm/llvm-project/pull/91364