[module] Finalize definitions for the end-user

Closes https://github.com/bytecodealliance/cranelift/issues/1288 by
calling `module.finalize_definitions` whenever `module.finish` is
called.

cranelift/module/src/module.rs

@@ -714,7 +714,8 @@ where
     /// Consume the module and return the resulting `Product`. Some `Backend`
     /// implementations may provide additional functionality available after
     /// a `Module` is complete.
-    pub fn finish(self) -> B::Product {
+    pub fn finish(mut self) -> B::Product {
+        self.finalize_definitions();
         self.backend.finish()
     }
 }