refactor(perf-loader): remove unused reference

lib/builder/builder.js

@@ -425,7 +425,7 @@ export default class Builder {
   }
 
   async webpackBuild() {
-    this.perfLoader = new PerfLoader(this)
+    this.perfLoader = new PerfLoader(this.options)
 
     const compilersOptions = []
 

lib/builder/webpack/utils/perf-loader.js

@@ -6,9 +6,8 @@ import threadLoader from 'thread-loader'
 // https://github.com/webpack-contrib/cache-loader
 
 export default class PerfLoader {
-  constructor(builder) {
-    this.builder = builder
-    this.options = builder.options
+  constructor(options) {
+    this.options = options
 
     this.workerPools = {
       js: {