Always insert the entry EBB before translating any WASM.

The FuncEnvironment callbacks (make_global in particular) may need to
insert code in the entry EBB. We need to make sure the entry EBB has
been inserted in the layout before making those callbacks.

lib/frontend/src/frontend.rs

@@ -373,7 +373,7 @@ where
     }
 
     /// Make sure that the current EBB is inserted in the layout.
-    fn ensure_inserted_ebb(&mut self) {
+    pub fn ensure_inserted_ebb(&mut self) {
         let ebb = self.position.ebb;
         if self.builder.ebbs[ebb].pristine {
             if !self.func.layout.is_ebb_inserted(ebb) {