[llvm] [lit] Add --report-failures-only option for lit test reports (PR #115439)

[James Henderson via llvm-commits]

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@@ -137,6 +137,10 @@ def main(builtin_params={}):
     print_results(discovered_tests, elapsed, opts)
 
     tests_for_report = selected_tests if opts.shard else discovered_tests
+    if opts.report_failures_only:
+        # Only report tests that failed
----------------
jh7370 wrote:

```suggestion
        # Only report tests that failed.
```
Nit: LLVM coding standards says to finish comments with a full stop.

https://github.com/llvm/llvm-project/pull/115439