Build JS module only in development mode (#62398)

Co-authored-by: kevin940726 <kevin940726@git.wordpress.org>
Co-authored-by: gziolo <gziolo@git.wordpress.org>

Author: kevin940726

bin/packages/build-worker.js

@@ -13,6 +13,8 @@ const postcss = require( 'postcss' );
  */
 const getBabelConfig = require( './get-babel-config' );
 
+const isDev = process.env.NODE_ENV === 'development';
+
 /**
  * Path to packages directory.
  *
@@ -27,10 +29,12 @@ const PACKAGES_DIR = path
  *
  * @type {Object}
  */
-const JS_ENVIRONMENTS = {
-	main: 'build',
-	module: 'build-module',
-};
+const JS_ENVIRONMENTS = isDev
+	? { module: 'build-module' }
+	: {
+			main: 'build',
+			module: 'build-module',
+	  };
 
 /**
  * Promisified fs.readFile.

package.json

@@ -274,8 +274,8 @@
 		"build:plugin-zip": "bash ./bin/build-plugin-zip.sh",
 		"clean:package-types": "tsc --build --clean && rimraf \"./packages/*/build-types\"",
 		"clean:packages": "rimraf \"./packages/*/@(build|build-module|build-style)\"",
-		"dev": "npm run build:packages && concurrently \"wp-scripts start\" \"npm run dev:packages\"",
-		"dev:packages": "concurrently \"node ./bin/packages/watch.js\" \"tsc --build --watch\"",
+		"dev": "cross-env NODE_ENV=development npm run build:packages && concurrently \"wp-scripts start\" \"npm run dev:packages\"",
+		"dev:packages": "cross-env NODE_ENV=development concurrently \"node ./bin/packages/watch.js\" \"tsc --build --watch\"",
 		"distclean": "git clean --force -d -X",
 		"docs:api-ref": "node ./bin/api-docs/update-api-docs.js",
 		"docs:blocks": "node ./bin/api-docs/gen-block-lib-list.js",