[MODULARIZE=instance] Enable direct running of output under v8 (#24337)

diff --git a/.circleci/config.yml b/.circleci/config.yml
index 6835781..7e3f65f 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -649,6 +649,7 @@
             wasmfs.test_fs_llseek_rawfs
             wasmfs.test_freetype
             minimal0.test_utf
+            instance.test_async_hello_v8
             "
   test-wasm2js1:
     environment:
diff --git a/src/postamble.js b/src/postamble.js
index 904c1ed..d64c7f9 100644
--- a/src/postamble.js
+++ b/src/postamble.js
@@ -341,6 +341,13 @@
 }
 #endif
 
+#if ENVIRONMENT_MAY_BE_SHELL
+if (ENVIRONMENT_IS_SHELL) {
+  // When run in a shell we run `init` immediately.
+  await init();
+}
+#endif
+
 #else
 preInit();
 run();