enable checkJS

build/npm/postinstall.js

@@ -49,6 +49,7 @@ extensions.forEach(extension => yarnInstall(`extensions/${extension}`));
 function yarnInstallBuildDependencies() {
 	// make sure we install the deps of build/lib/watch for the system installed
 	// node, since that is the driver of gulp
+	//@ts-ignore review
 	const env = Object.assign({}, process.env);
 	const watchPath = path.join(path.dirname(__dirname), 'lib', 'watch');
 	const yarnrcPath = path.join(watchPath, '.yarnrc');