run grunt from different directory for building submodule

gruntfile.js

module.exports = function(grunt) {
  'use strict';
  var parent_module = '../../node_modules/';
  grunt.loadTasks(parent_module + 'grunt-contrib-watch/tasks');
  grunt.loadTasks(parent_module+'grunt-contrib-concat/tasks');
  grunt.loadTasks(parent_module+'grunt-contrib-uglify/tasks');

  grunt.initConfig({
    pkg: grunt.file.readJSON('../../package.json'),
    concat: {
      options: {
        separator: '//#######################################################\n'
      },
      dist: {
        src: [
          '**/*.module.js',
          '**/*.state.js',
          '**/*.config.js',
          '**/*.run.js',
          '**/*.js'
        ],
        dest: '../../dist/<%= pkg.name %>-submodule.js'
      }
    },
    uglify: {
      options: {
        banner: '/*! <%= pkg.name %>-submodule - v <%= pkg.version %> - by <%= pkg.author %>' +
        ' <%= grunt.template.today("dd-mmmm-yyyy")%> */\n',
        sourceMap: true
      },
      dist: {
        files: {
          '../../dist/<%= pkg.name %>-submodule.min.js': ['<%= concat.dist.dest %>']
        }
      }
    },
    watch: {
      js: {
        files: ['<%= concat.dist.src %>']
      },
      options: {
        nospawn: true
      }
      // tasks: ['build'] not work here
    }
  });

  grunt.event.on('watch', function(action, filepath, target) {
    grunt.log.writeln(target + ': ' + filepath + ' has ' + action+' defined by enter on grunt event');
    // achievable via 
    grunt.task.run('build');
  });

  grunt.registerTask('build', ['concat', 'uglify']);
  grunt.registerTask('default', ['watch']);
};

My env :

node: v4.2.6
npm: 3.7.4
"grunt": "^0.4.5",
"grunt-contrib-concat": "^0.5.1",
"grunt-contrib-uglify": "^0.11.0",
"grunt-contrib-watch": "^0.6.1",