[llvm] [AArch64] Roundup newly allocated stack size according -mstack-alignment (PR #100859)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

I guess my biggest question here is, do we actually want this?  The instruction set enforces that the stack must be 16-byte aligned, and there isn't any existing code that assumes higher stack alignment.  So this would only be useful for some closed system which for some strange reason had a lot of stack variables marked alignas(32).  Which seems way too obscure to be worth worrying about.

I'd suggest "fixing" #97268 by just rejecting the option.

https://github.com/llvm/llvm-project/pull/100859