Ngmin has been deprecated and you are told this every time you do an npm install on the project.
Git Issue that resolves this for new generated projects from yeoman
Why to migrate.
ng-min is deprecated so it is no longer supported.
ng-min is slow. For a mature medium-sized angularjs app ng-min was taking 50 seconds of the build time. Running with ng-annotate instead it now takes only 2 seconds to do the same thing.
Now the uglify task takes the most time of the build at 8 seconds against the 2 seconds needed for the ngannotate task.
A savings of 48 seconds a build.
Built Machine spec:
OSX 10.9.5 with 3.2 GHz with 24 GB of ram. No modifications have been made to the memory settings for grunt or node.