[clang] [PAC][clang] Use `Error` behavior for ptrauth module flags (PR #189923)

[Daniil Kovalev via cfe-commits]

kovdan01 wrote:

This was tested on pauthtest buildbot: https://lab.llvm.org/buildbot/#/builders/227/builds/547
This includes building and running a large subset of llvm-test-suite

https://github.com/llvm/llvm-project/pull/189923