[llvm] [GlobalISel] Add support for lowering byref attribute (PR #96733)

[Gábor Spaits via llvm-commits]

spaits wrote:

I would also like to see some tests, to see the PRs effect on the behavior. Otherwise it looks good to me.

When I have implemented the first phase of indirect parameter passing and did some debugging and I have recognized that in case of indirect parameter passing the `byRef` attribute of the flag is not set. I have also extended the `addFlagsUsingAttrFn` function to recognize the attribute for the debugging.

https://github.com/llvm/llvm-project/pull/96733