[clang] Add ability for clang-format-diff to exit with non-0 status (PR #70883)

[Owen Pan via cfe-commits]

================
@@ -95,6 +95,12 @@ def main():
         default="clang-format",
         help="location of binary to use for clang-format",
     )
+    parser.add_argument(
+        "-non-zero-exit-code",
+        action="store_true",
+        default=False,
+        help="exit with a non-zero status if formatting changes are necessary",
+    )
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owenca wrote:

```suggestion
```

https://github.com/llvm/llvm-project/pull/70883