[llvm] [PowerPC][AIX] Specify pointer info and alignment for stack store (PR #144526)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> I guess getStackAlign() is the right alignment here. In general, we don't guarantee the stack pointer has "stack alignment" at any particular point; 

There is also getTransientStackAlign which I've never understood


https://github.com/llvm/llvm-project/pull/144526