fix: set 'threads' of eslint-webpack-plugin by 'options.parallel'

Author: fangbinwei

packages/@vue/cli-plugin-eslint/index.js

@@ -24,6 +24,9 @@ module.exports = (api, options) => {
         cacheLocation: api.resolve('node_modules/.cache/.eslintcache'),
         // plugin options
         context: cwd,
+        threads: process.env.NODE_ENV === 'production'
+          ? options.parallel
+          : false,
         emitWarning: allWarnings,
         emitError: allErrors,
         eslintPath: path.dirname(