[llvm] [aarch64] Mix the frame pointer with the stack cookie when protecting the stack (PR #161114)

[Hans Wennborg via llvm-commits]

zmodem wrote:

Thanks @luporl for flagging this and reverting!

This change broke some Win/ARM64 tests in Chromium too (https://crbug.com/472955048) but we were slow to track it down due to the holidays. Please keep me in the loop when this is ready for relanding so we can try it out beforehand.

https://github.com/llvm/llvm-project/pull/161114