[clang] [llvm] Handle leading underscores in update_cc_test_checks.py (PR #121800)

[Alexander Richardson via llvm-commits]

================
@@ -122,6 +122,11 @@ def parse_clang_ast_json(node, loc, search):
         if search is None:
             search = spell
         mangled = node.get("mangledName", spell)
+        # Strip leading underscore from globals, so the name matches the LLVM one
----------------
arichardson wrote:

```suggestion
        # Clang's AST dump includes the globals prefix, but when Clang emits LLVM IR this is not included and instead added as part of the asm output.
        # Strip it from the mangled name of globals when needed (see DataLayout::getGlobalPrefix()).
```

Maybe add a more detailed comment along these lines?

https://github.com/llvm/llvm-project/pull/121800