perf: use native util.promisify instead of pify

https://nodejs.org/api/util.html#util_util_promisify_original

lib/builder/builder.js

@@ -1,8 +1,8 @@
+import { promisify } from 'util'
 import _ from 'lodash'
 import chokidar from 'chokidar'
 import fs, { remove, readFile, writeFile, mkdirp, existsSync } from 'fs-extra'
 import hash from 'hash-sum'
-import pify from 'pify'
 import webpack from 'webpack'
 import serialize from 'serialize-javascript'
 import { join, resolve, basename, extname, dirname } from 'path'
@@ -22,7 +22,7 @@ import { Options } from 'common'
 const debug = Debug('nuxt:build')
 debug.color = 2 // Force green color
 
-const glob = pify(Glob)
+const glob = promisify(Glob)
 
 export default class Builder {
   constructor(nuxt) {
@@ -519,7 +519,7 @@ export default class Builder {
     debug('Adding webpack middleware...')
 
     // Create webpack dev middleware
-    this.webpackDevMiddleware = pify(webpackDevMiddleware(compiler, Object.assign({
+    this.webpackDevMiddleware = promisify(webpackDevMiddleware(compiler, Object.assign({
       publicPath: this.options.build.publicPath,
       stats: this.webpackStats,
       noInfo: true,
@@ -527,9 +527,9 @@ export default class Builder {
       watchOptions: this.options.watchers.webpack
     }, this.options.build.devMiddleware)))
 
-    this.webpackDevMiddleware.close = pify(this.webpackDevMiddleware.close)
+    this.webpackDevMiddleware.close = promisify(this.webpackDevMiddleware.close)
 
-    this.webpackHotMiddleware = pify(webpackHotMiddleware(compiler, Object.assign({
+    this.webpackHotMiddleware = promisify(webpackHotMiddleware(compiler, Object.assign({
       log: false,
       heartbeat: 10000
     }, this.options.build.hotMiddleware)))

test/cli.test.js

@@ -1,11 +1,11 @@
+import { promisify } from 'util'
 import test from 'ava'
 import { resolve, sep } from 'path'
 import rp from 'request-promise-native'
 import { Utils } from '../index.js'
-import pify from 'pify'
 import { exec, spawn } from 'child_process'
 
-const execify = pify(exec, { multiArgs: true })
+const execify = promisify(exec, { multiArgs: true })
 const rootDir = resolve(__dirname, 'fixtures/basic')
 
 const port = 4011

test/dll.test.js

@@ -1,11 +1,11 @@
+import { promisify } from 'util'
 import test from 'ava'
 import { resolve } from 'path'
 import fs from 'fs'
-import pify from 'pify'
 import stdMocks from 'std-mocks'
 import { Nuxt, Builder } from '../index.js'
 
-const readFile = pify(fs.readFile)
+const readFile = promisify(fs.readFile)
 const rootDir = resolve(__dirname, './fixtures/dll')
 const dllDir = resolve(rootDir, '.cache/client-dll')
 

test/dynamic-routes.test.js

@@ -1,10 +1,10 @@
 import test from 'ava'
 import { resolve } from 'path'
 import fs from 'fs'
-import pify from 'pify'
 import { Nuxt, Builder } from '../index.js'
+import { promisify } from 'util'
 
-const readFile = pify(fs.readFile)
+const readFile = promisify(fs.readFile)
 
 test.before('Init Nuxt.js', async t => {
   const nuxt = new Nuxt({