cranelift: Fix implicit pointer argument register use (#5301)

* Fix arg handling to write to VRegs instead of physical regs

* Make is_included_in_clobbers required, and handle Args on x64 and riscv64

cranelift/codegen/src/isa/s390x/inst/mod.rs

@@ -1109,6 +1109,7 @@ impl MachInst for Inst {
         // half-caller-save, half-callee-save SysV ABI for some vector
         // registers.
         match self {
+            &Inst::Args { .. } => false,
             &Inst::Call { ref info, .. } => info.caller_callconv != info.callee_callconv,
             &Inst::CallInd { ref info, .. } => info.caller_callconv != info.callee_callconv,
             _ => true,