[SimpleJIT] When finalizing multiple functions, make them all executable at the end. (#474)

Add `publish()` function to cranelift-module's `Backend` trait, which
allows `finalize_all()` to defer making memory executable until it
has finished all of the patching it needs to do.

lib/faerie/src/backend.rs

@@ -281,6 +281,10 @@ impl Backend for FaerieBackend {
         // Nothing to do.
     }
 
+    fn publish(&mut self) {
+        // Nothing to do.
+    }
+
     fn finish(self) -> FaerieProduct {
         FaerieProduct {
             artifact: self.artifact,