Fix a bug where the standalone static build Promise is resolved befor…

…e it actually completes

lib/core/src/server/build-static.js

@@ -41,26 +41,30 @@ export async function buildStaticStandalone(options) {
   }
 
   // compile all resources with webpack and write them to the disk.
-  logger.info('Building storybook ...');
-  const webpackCb = (err, stats) => {
-    if (err || stats.hasErrors()) {
-      logger.error('Failed to build the storybook');
-      // eslint-disable-next-line no-unused-expressions
-      err && logger.error(err.message);
-      // eslint-disable-next-line no-unused-expressions
-      stats && stats.hasErrors() && stats.toJson().errors.forEach(e => logger.error(e));
-      process.exitCode = 1;
-    }
-    logger.info('Building storybook completed.');
-  };
+  return new Promise((resolve, reject) => {
+    const webpackCb = (err, stats) => {
+      if (err || stats.hasErrors()) {
+        logger.error('Failed to build the storybook');
+        // eslint-disable-next-line no-unused-expressions
+        err && logger.error(err.message);
+        // eslint-disable-next-line no-unused-expressions
+        stats && stats.hasErrors() && stats.toJson().errors.forEach(e => logger.error(e));
+        process.exitCode = 1;
+        return reject(err);
+      }
+      logger.info('Building storybook completed.');
+      return resolve(stats);
+    };
 
-  const compiler = webpack(config);
+    logger.info('Building storybook ...');
+    const compiler = webpack(config);
 
-  if (watch) {
-    compiler.watch({}, webpackCb);
-  } else {
-    compiler.run(webpackCb);
-  }
+    if (watch) {
+      compiler.watch({}, webpackCb);
+    } else {
+      compiler.run(webpackCb);
+    }
+  });
 }
 
 export async function buildStatic({ packageJson, ...loadOptions }) {