Add a minimal SimpleJIT example program.

This minimally demonstrates usage of the API, and serves as a very small
testcase to test that the basic JIT mechanisms are working.

lib/faerie/src/backend.rs

@@ -277,10 +277,18 @@ impl Backend for FaerieBackend {
         // Nothing to do.
     }
 
+    fn get_finalized_function(&self, _func: &FaerieCompiledFunction) {
+        // Nothing to do.
+    }
+
     fn finalize_data(&mut self, _data: &FaerieCompiledData, _namespace: &ModuleNamespace<Self>) {
         // Nothing to do.
     }
 
+    fn get_finalized_data(&self, _data: &FaerieCompiledData) {
+        // Nothing to do.
+    }
+
     fn publish(&mut self) {
         // Nothing to do.
     }