[llvm] [PPC] Implement `areInlineCompatible` (PR #126562)

[Henry Jiang via llvm-commits]

mustartt wrote:

I think in general, there are a subset of target features where the having a subset of target features should be allowed: i.e. vector instructions that excludes floating points FMA, MMA, and other that can have noticeable side-effects in the program. But there definitely exists cases where we need to compare for strict equality, i.e. 
```
allow-unaligned-fp-access      - CPU does not trap on unaligned FP access.
```
where we should not inline a function that does not allow unaligned fp access into a caller that does. 

This is just one example, but there are probably a lot more.


https://github.com/llvm/llvm-project/pull/126562