Ember build for production took more than expected time

I'm developing an Ember application, in that application

Building application for production environment gives following warning during build process.

>>ember build --environment production
WARNING: Node v7.2.1 is not tested against Ember CLI on your platform. We recommend that you use the most-recent "Active LTS" version of Node.js.
/ Building[WARN] `assets/vendor.js` took: 27201ms (more than 20,000ms)
cleaning up...
Built project successfully. Stored in "dist/".
File sizes:
 - dist/assets/vendor-55a426e75e5239020a12bb7bfc6ffc2a.js: 759.74 KB (195.13 KB gzipped)
 - dist/assets/vendor-d41d8cd98f00b204e9800998ecf8427e.css: 0 B

i want to suppress these waning messages, for this i tried --silent with command.

ember build --environment production --silent

Still im getting following warning:

[WARN] `assets/vendor.js` took: 27201ms (more than 20,000ms)

cam some one tell me how to suppress this warning or fix this?