Although 32-bit targets are currently not officially supported, add a type conversion in the AllocMemOp lowering when calling the `malloc` function on 32-bit targets. This fixes a type mismatch, and this fix makes it easier to potentially support such targets in the future. This involves making sure the `LLVMTypeConverter` has the necessary information to know the target bit width. Co-authored-by: Valentin Clement (バレンタイン クレメン) <clementval@gmail.com>