[Bug Report] NUXT下，执行nuxt build报错

### VUX version
2.9.2

### OS/Browsers version
win10

### Vue version
2.5.17-beta.0

### Code

```html
下面是nuxt.config.js的配置

const path = require('path')
const vuxLoader = require('vux-loader')
module.exports = {

/*
** Headers of the page
*/
head: {
title: 'teldmobile',
meta: [
{ charset: 'utf-8' },
{ name: 'viewport', content: 'width=device-width, initial-scale=1' },
{ hid: 'description', name: 'description', content: 'Nuxt.js project' }
],

link: [
{ rel: 'icon', type: 'image/x-icon', href: '/favicon.ico' }
]
},
css: [
'vux/src/styles/reset.less',
'vux/src/styles/1px.less'
],
plugins: [
{
src: '~/plugins/vux-plugins',
ssr: false
},
{
src: '~/plugins/vux-components',
ssr: true
}
],
/*
** Customize the progress bar color
*/
loading: { color: '#3B8070' },
/*
** Build configuration
*/
build: {
/*
** Run ESLint on save
*/
// extend (config, { isDev, isClient }) {
// if (isDev && isClient) {
// config.module.rules.push({
// enforce: 'pre',
// test: /\.(js|vue)$/,
// loader: 'eslint-loader',
// exclude: /(node_modules)/
// })
// }
// }

extend(config, { isDev, isClient }) {

const configs = vuxLoader.merge(config, {
options: {
ssr: true
},
plugins: ['vux-ui', {
name: 'less-theme',
path: path.join(__dirname, './styles/theme.less')
}]
})

return configs
}
},
router: {
middleware: 'teld'
},
modules: [
//'@nuxtjs/axios',
],

axios: {
// proxyHeaders: false
}
}

```

### Steps to reproduce
执行nuxt build

### What is Expected?
希望执行nuxt build能正常通过编译

### What is actually happening?

ERROR in 0.nuxt.bundle.e2e23cd8c3f50b85efa8.js from UglifyJs
Unexpected token: punc ()) [./~/vux/src/components/inline-calendar/props.js:1,15][0.nuxt.bundle.e2e23cd8c3f50b85efa8.js:46,58]

ERROR in vendor.bundle.b674866f0b79219627ec.js from UglifyJs
Unexpected token name «i», expected punc «;» [./~/vux/src/libs/plugin_helper.js:5,11][vendor.bundle.b674866f0b79219627ec.js:8706,11]
Error: Webpack build exited with errors
at C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\dist\nuxt.js:1161:44
at C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\webpack\lib\Compiler.js:272:15
at Compiler.emitRecords (C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\webpack\lib\Compiler.js:367:37)
at C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\webpack\lib\Compiler.js:265:12
at C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\webpack\lib\Compiler.js:360:11
at next (C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\tapable\lib\Tapable.js:154:11)
at Compiler.compiler.plugin (C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\webpack\lib\performance\SizeLimitsPlugin.js:99:4)
at Compiler.applyPluginsAsyncSeries1 (C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\tapable\lib\Tapable.js:158:13)
at Compiler.afterEmit (C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\webpack\lib\Compiler.js:357:8)
at Compiler. (C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\webpack\lib\Compiler.js:352:14)
at C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\async\dist\async.js:421:16
at iteratorCallback (C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\async\dist\async.js:998:13)
at C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\async\dist\async.js:906:16
at D:\NUXT\TeldMobile\node_modules\graceful-fs\graceful-fs.js:43:10
at C:\Users\chendong\AppData\Roaming\npm\node_modules\nuxt\node_modules\graceful-fs\graceful-fs.js:43:10
at FSReqWrap.oncomplete (fs.js:145:20)