[compiler-rt] [compiler-rt][ARM] Add missing PACBTI support to assembly aeabi functions (PR #142400)

[Victor Campos via llvm-commits]

vhscampos wrote:

> The other possibility I thought about was to have a macro that conditionally expanded to `, r12` or nothing depending on whether PAC was being used. That could be used in the save list for push, however I don't think there's any precedent for that in compiler-rt so it's probably not a good idea.

I also thought of that, however the register list argument for push and pop must be in order, therefore `r12` has to come before `lr`. As far as I could tell, this kind of maneuvering is not possible with the preprocessor machinery.

https://github.com/llvm/llvm-project/pull/142400