old_contents: {
     'targets':[
          {
              'target_name':'start_first',
              'type':'executable',
              'dependencies':[],
              'defines':[],
              'include_dirs':[],
              'sources':[
                  'start_first/opengl_first.c',
              ],
              'libraries':[
                  '-lGLU -lGL -lglut'
              ],
              'conditions':[]
          }
      ],
  }
  
new_contents: {
     'targets':[
          {
              'target_name':'start_first',
              'type':'executable',
              'dependencies':[],
              'defines':[],
              'include_dirs':[],
              'sources':[
                  'start_first/opengl_first.c',
              ],
              'libraries':[
                  '-lGLU -lGL -lglut'
              ],
              'conditions':[]
          },
          {
              'target_name':'test_vertex',
              'type':'executable',
              'dependencies':[],
              'defines':[],
              'include_dirs':[],
              'sources':[
                  'test_vertex/test_vertex.c',
              ],
              'libraries':[
                  '-lGLU -lGL -lglut'
              ],
              'conditions':[]
          }
      ],
  }
  
subject: add test_vertex mode