webpack安装，npm WARN optional SKIPPING OPTIONAL DEPENDENCY，npm WARN notsup SKIPPING OPTIONAL DEPENDENCY警告

npm install webpack -g//全局安装webpack

电脑上安装完后：

其中有两个警告：

npm WARN optional SKIPPING OPTIONAL DEPENDENCY:fsevents@1.2.7 (node_modules\webpack\node_modules\fsevents):

npm WARN notsup SKIPPING OPTIONAL DEPENDENCY:  Unsupported platform for fsevents@1.2.7: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})
fsevent是mac系统的，在win或者Linux下使用，会不支持fsevents平台，所以产生了警告