[libcxx] [llvm] [libc++][CI] Reenables clang-tidy. (PR #90077)

[Louis Dionne via llvm-commits]

================
@@ -64,6 +64,26 @@ if(NOT HAS_CLANG_TIDY_HEADERS)
                  "clang-tidy headers are not present.")
   return()
 endif()
+
+# The clangTidy plugin uses C++20, when using stdlibc++ verify the version is correct.
+# Note it has not been tested whether version 11 works.
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/test.cpp" "
+#include <version>
+#if defined(_GLIBCXX_RELEASE) && _GLIBCXX_RELEASE < 12
+  # error The stdlibc++ version is too old.
----------------
ldionne wrote:

```suggestion
  # error The libstdc++ version is too old.
```

https://github.com/llvm/llvm-project/pull/90077