Allow -n no build option and allow ~x86
Allow -n no build option and allow ~x86

Review URL: http://codereview.chromium.org/801006

coreos/dev-util,mgireesh05/dev-util,coreos/dev-util,mgireesh05/dev-util,marineam/coreos-dev-util,coreos/dev-util,mgireesh05/dev-util,marineam/coreos-dev-util