fix -Zsanitizer=kcfi on #[naked] functions

And more broadly only codegen `InstanceKind::Item` using the naked
function codegen code. Other instance kinds should follow the normal
path.

Author: folkertdev

src/driver/aot.rs

@@ -530,8 +530,12 @@ fn codegen_cgu_content(
     for (mono_item, item_data) in mono_items {
         match mono_item {
             MonoItem::Fn(instance) => {
-                if tcx.codegen_fn_attrs(instance.def_id()).flags.contains(CodegenFnAttrFlags::NAKED)
-                {
+                // Other `InstanceKind`s (e.g. `ReifyShim` generated by indirect calls) should be
+                // codegened like a normal function.
+                let is_item_instance = matches!(instance.def, InstanceKind::Item(_));
+
+                let flags = tcx.codegen_fn_attrs(instance.def_id()).flags;
+                if is_item_instance && flags.contains(CodegenFnAttrFlags::NAKED) {
                     rustc_codegen_ssa::mir::naked_asm::codegen_naked_asm(
                         &mut GlobalAsmContext { tcx, global_asm: &mut cx.global_asm },
                         instance,