cranelift-object: move relocation processing to finish

This removes the need to call `finalize_definitions` for cranelift-object.
`finalize_definitions` is only intended for backends that produce
finalized functions and data objects, which cranelift-object does not.

cranelift/module/src/backend.rs

@@ -146,7 +146,7 @@ where
 
     /// Consume this `Backend` and return a result. Some implementations may
     /// provide additional functionality through this result.
-    fn finish(self) -> Self::Product;
+    fn finish(self, namespace: &ModuleNamespace<Self>) -> Self::Product;
 }
 
 /// Default names for `ir::LibCall`s. A function by this name is imported into the object as