[clang] [PAC] Add support for __ptrauth type qualifier (PR #100830)

[Akira Hatanaka via cfe-commits]

================
@@ -104,6 +104,7 @@ FEATURE(thread_sanitizer, LangOpts.Sanitize.has(SanitizerKind::Thread))
 FEATURE(dataflow_sanitizer, LangOpts.Sanitize.has(SanitizerKind::DataFlow))
 FEATURE(scudo, LangOpts.Sanitize.hasOneOf(SanitizerKind::Scudo))
 FEATURE(ptrauth_intrinsics, LangOpts.PointerAuthIntrinsics)
+FEATURE(ptrauth_qualifier, LangOpts.PointerAuthIntrinsics)
----------------
ahatanak wrote:

`__has_feature(ptrauth_qualifier)` is being used in more than a few internal projects and using `EXTENSION` instead of `FEATURE` here would break them.

Doesn't `clang/docs/LanguageExtensions.rst` state that we can use `__has_feature` to check for compiler features not related to the language standard? https://clang.llvm.org/docs/LanguageExtensions.html#has-feature-and-has-extension

https://github.com/llvm/llvm-project/pull/100830