Fix bug from PR #1082

See: https://github.com/vuejs-templates/webpack/pull/1082/files#r154501049

Author: LinusBorg

template/build/webpack.base.conf.js

@@ -8,7 +8,7 @@ function resolve (dir) {
   return path.join(__dirname, '..', dir)
 }
 
-const lintingRule = {
+const createLintingRule = () => ({
   test: /\.(js|vue)$/,
   loader: 'eslint-loader',
   enforce: 'pre',
@@ -17,7 +17,7 @@ const lintingRule = {
     formatter: require('eslint-friendly-formatter'),
     emitWarning: !config.dev.showEslintErrorsInOverlay
   }
-}
+})
 
 module.exports = {
   context: path.resolve(__dirname, '../'),
@@ -43,7 +43,7 @@ module.exports = {
   module: {
     rules: [
       {{#lint}}
-      ...(config.dev.useEslint ? [lintingRule] : []),
+      ...(config.dev.useEslint ? [createLintingRule()] : []),
       {{/lint}}
       {
         test: /\.vue$/,