[CI] adjust the undef warning regex so it doesn't catch %undef in .ll files

Author: nunoplopes

llvm/utils/git/code-format-helper.py

@@ -387,13 +387,11 @@ def format_run(self, changed_files: List[str], args: FormatArgs) -> Optional[str
         for file in re.split("^diff --git ", stdout, 0, re.MULTILINE):
             filename = re.match("a/([^ ]+)", file.splitlines()[0])[1]
             if filename.endswith(".ll"):
-                undef_regex = r"\bundef\b"
+                undef_regex = r"(?<!%)\bundef\b"
             else:
                 undef_regex = r"UndefValue::get"
             # search for additions of undef
-            if re.search(
-                r"^[+](?!\s*#\s*).*(" + undef_regex + r")", file, re.MULTILINE
-            ):
+            if re.search(r"^[+].*" + undef_regex, file, re.MULTILINE):
                 files.append(filename)
 
         if not files: