Previously, arguments with `ABIArgInfo::Indirect` would not be given alignment information if it wasn't `byval`. This could prevent certain optimizations, such as those guarded by `isDereferenceableAndAlignedPointer` checks. The missing dereferenceability information is pointed out in https://github.com/llvm/llvm-project/issues/129337, for example. This PR will fix the first half of this problem, which is emitting alignment information. Dereferenceability information will be added in a subsequent PR.