ci: fix travis environment to build es2015 distro (#13976)

scripts/ci-lite/env.sh

@@ -58,6 +58,11 @@ if [[ ${TRAVIS} ]]; then
   # more info: https://docs.travis-ci.com/user/languages/javascript-with-nodejs#Node.js-v4-(or-io.js-v3)-compiler-requirements
   export CXX=g++-4.8
 
+  # Build ES2015 distro only in the e2e job (don't need to slow down other jobs)
+  if [ "${CI_MODE}" = "e2e" ]; then
+    export EXPERIMENTAL_ES2015_DISTRO=1
+  fi
+
   # Used by karma and karma-chrome-launcher
   # In order to have a meaningful SauceLabs badge on the repo page,
   # the angular2-ci account is used only when pushing commits to master;