[clang] [Clang] Take libstdc++ into account during GCC detection (PR #145056)

[Aaron Ballman via cfe-commits]

================
@@ -874,4 +874,9 @@ def warn_drv_openacc_without_cir
     : Warning<"OpenACC directives will result in no runtime behavior; use "
               "-fclangir to enable runtime effect">,
       InGroup<SourceUsesOpenACC>;
+
+def warn_drv_gcc_install_dir_libstdcxx : Warning<
+    "future releases of the clang compiler will prefer GCC installations "
----------------
AaronBallman wrote:

```suggestion
    "future releases of Clang will prefer GCC installations "
```

https://github.com/llvm/llvm-project/pull/145056