message: don't try to build ghost packages
diff: @@ -82,6 +82,10 @@ function buildBrowserPackage(p) {
  const srcDir = path.resolve(p, SRC_DIR);
  const pkgJsonPath = path.resolve(p, 'package.json');
  + if (!fs.existsSync(pkgJsonPath)) {
  + return;
  + }
  +
  const {browser} = require(pkgJsonPath);
  if (browser) {
  if (browser.indexOf(BUILD_ES5_DIR) !== 0) {
  