[clang-tools-extra] [clang-tidy] Add avoid-pragma-once. (PR #140388)

[Baranov Victor via cfe-commits]

================
@@ -0,0 +1,12 @@
+.. title:: clang-tidy - portability-avoid-pragma-once
+
+portability-avoid-pragma-once
+=============================
+
+This check catches pragma once usage.
+
+For example:
+
+```
----------------
vbvictor wrote:

use `.. code-block:: c++` for code, see other .rst docs for reference

https://github.com/llvm/llvm-project/pull/140388