wasm-merge: Validate at the very end (#7962)

Doing this at the end can catch more issues. For finding issues in the
middle, pass-debug mode already does that.

Author: kripken

src/tools/wasm-merge.cpp

@@ -778,14 +778,6 @@ Input source maps can be specified by adding an -ism option right after the modu
     }
   }
 
-  // If we didn't validate after each merged module, validate once at the very
-  // end. This won't catch problems at the earliest point, but is still useful.
-  if (!PassRunner::getPassDebug() && options.passOptions.validate &&
-      !WasmValidator().validate(merged)) {
-    std::cout << merged << '\n';
-    Fatal() << "error in validating final merged";
-  }
-
   // Fuse imports and exports now that everything is all together in the merged
   // module.
   fuseImportsAndExports(options.passOptions);
@@ -808,6 +800,13 @@ Input source maps can be specified by adding an -ism option right after the modu
     passRunner.run();
   }
 
+  // Without pass-debug mode, validate once at the very end.
+  if (!PassRunner::getPassDebug() && options.passOptions.validate &&
+      !WasmValidator().validate(merged)) {
+    std::cout << merged << '\n';
+    Fatal() << "error in validating final merged";
+  }
+
   // Output.
   if (options.extra.count("output") > 0) {
     ModuleWriter writer(options.passOptions);