fix(typescript): fix ts + modern mode

close #1577

Author: yyx990803

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

@@ -24,7 +24,8 @@ module.exports = (api, options) => {
       loader: 'cache-loader',
       options: api.genCacheConfig('ts-loader', {
         'ts-loader': require('ts-loader/package.json').version,
-        'typescript': require('typescript/package.json').version
+        'typescript': require('typescript/package.json').version,
+        modern: !!process.env.VUE_CLI_MODERN_BUILD
       }, 'tsconfig.json')
     })