使用call调用yarn安装包，防止批处理退出

使用set设置环境变量，代替cross-env

branch是变量

call yarn
echo install done
set MODE_ENV=jenkins 
set BUILD_PATH=/temp/air/%branch% 
set PUBLIC_URL=/air/%branch% 
set GENERATE_SOURCEMAP=false 
node scripts/build.js

原package.json脚本：

"scripts": {
    "build_jenkins": "cross-env MODE_ENV=jenkins BUILD_PATH=/temp/air/master PUBLIC_URL=/air/master GENERATE_SOURCEMAP=false node scripts/build.js"
  }