also repsect external autoprefixer options

Author: yyx990803

lib/style-rewriter.js

@@ -2,6 +2,7 @@ var postcss = require('postcss')
 var selectorParser = require('postcss-selector-parser')
 var hash = require('hash-sum')
 var loaderUtils = require('loader-utils')
+var assign = require('object-assign')
 
 var currentId
 var addId = postcss.plugin('add-id', function () {
@@ -42,7 +43,12 @@ module.exports = function (css) {
     processors.push(addId)
   }
   if (autoprefixOptions !== false) {
-    autoprefixOptions = autoprefixOptions || { remove: false }
+    autoprefixOptions = assign(
+      {},
+      // also respect autoprefixer-loader options
+      this.options.autoprefixer,
+      autoprefixOptions
+    )
     var autoprefixer = require('autoprefixer')(autoprefixOptions)
     processors.push(autoprefixer)
   }