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

[Anton Korobeynikov via cfe-commits]

asl wrote:

> Was there an RFC for this? I ask because it's introducing another qualifier and that has broad impacts on things beyond Clang like libc++, etc so we really need buy-in from a wider range of the community than will likely see this PR.

Just my 2 cents from downstream experience: the explicit qualifier is a great help for runtime library developers. As it makes explicit what is signed, what is not. And compiler ensures that all potential sensitive places are handled. Also, using qualifiers is much more convenient than explicit builtin calls :)

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