[clang] [PAC][clang] Fix ptrauth module flags behavior (PR #204226)

[Daniil Kovalev via cfe-commits]

kovdan01 wrote:

Ensured that pauthtest buildbot run succeeds with these changes: https://lab.llvm.org/buildbot/#/builders/227/builds/2622

https://github.com/llvm/llvm-project/pull/204226