[clang] allow use of ptrauth module from no_undeclared_includes system modules (PR #88432)

[Ian Anderson via cfe-commits]

ian-twilightcoder wrote:

Upstream from Apple, followup for https://github.com/llvm/llvm-project/pull/65996. Allows Apple's Darwin module to include ptrauth.h without declaring a `use`.

https://github.com/llvm/llvm-project/pull/88432