Mark scalar layout unions so that backends that do not support partially initialized scalars can special case them.

compiler/rustc_codegen_cranelift/src/common.rs

@@ -21,7 +21,7 @@ pub(crate) fn pointer_ty(tcx: TyCtxt<'_>) -> types::Type {
 }
 
 pub(crate) fn scalar_to_clif_type(tcx: TyCtxt<'_>, scalar: Scalar) -> Type {
-    match scalar.value {
+    match scalar.primitive() {
         Primitive::Int(int, _sign) => match int {
             Integer::I8 => types::I8,
             Integer::I16 => types::I16,