[llvm] [FileCheck] improve prefix validation (PR #92248)

[Thomas Preud'homme via llvm-commits]

================
@@ -2486,6 +2489,14 @@ static bool ValidatePrefixes(StringRef Kind, StringSet<> &UniquePrefixes,
              << "check and comment prefixes: '" << Prefix << "'\n";
       return false;
     }
+    for (StringRef Directive : Directives) {
+      if (Prefix.ends_with(Directive)) {
+        errs() << "error: supplied " << Kind << " prefix must not ends with "
----------------
RoboTux wrote:

```suggestion
        errs() << "error: supplied " << Kind << " prefix must not end with "
```

https://github.com/llvm/llvm-project/pull/92248