Add cfg if around cheri specific code

crates/runtime/src/instance.rs

@@ -344,10 +344,14 @@ impl Instance {
     }
 
     unsafe fn write_defined_memory(&self, mem_ptr: *mut VMMemoryDefinition, mem: VMMemoryDefinition) {
-        // First we write the whole thing. If we are on cheri, we then need to write the capability
-        // carrying pointer using inline assembly
-        let base = mem.base;
-        let current_length = mem.current_length.load(Ordering::Acquire);
+        cfg_if::cfg_if! {
+            if #[cfg(all(target_arch = "aarch64", feature = "cheri"))] {
+                // First we write the whole thing. If we are on cheri, we then need to write the capability
+                // carrying pointer using inline assembly
+                let base = mem.base;
+                let current_length = mem.current_length.load(Ordering::Acquire);
+            }
+        }
 
         ptr::write(mem_ptr, mem);
         cfg_if::cfg_if! {