[clang] [clang-tools-extra] [clang-tidy] Add SARIF output to clang-tidy (PR #219182)

[Zeyi Xu via cfe-commits]

================
@@ -754,7 +773,8 @@ int clangTidyMain(int argc, const char **argv) {
   unsigned WErrorCount = 0;
 
   handleErrors(Errors, Context, DisableFixes ? FB_NoFix : Behaviour,
-               WErrorCount, BaseFS);
+               WErrorCount, BaseFS, SarifOS.get(),
+               SarifOS && SarifExport == "-");
----------------
zeyi2 wrote:

Thanks for handling the regular text diagnostics when SARIF owns stdout!

Sorry that I missed a similar case before. There is still another output conflict with `--export-fixes=-`:

```cpp
struct A { A(int) {} };
```

```
clang-tidy -checks='-*,google-explicit-constructor' \
  -sarif-export=- -export-fixes=- input.cpp -- > output.txt
```

This exits with code 0, but `output.txt` contains both YAML and JSON.

Could we reject this combination before running the checks, or otherwise ensure only one exporter writes to stdout?

https://github.com/llvm/llvm-project/pull/219182