modern mode doesn't work when parallel be false

[lili21]

Version

3.2.1

Reproduction link

https://github.com/lili21/vue-cli-issue

Environment info

Environment Info:

  System:
    OS: macOS 10.14
    CPU: (8) x64 Intel(R) Core(TM) i7-4870HQ CPU @ 2.50GHz
  Binaries:
    Node: 8.11.1 - /usr/local/bin/node
    Yarn: 1.12.1 - /usr/local/bin/yarn
    npm: 6.4.1 - /usr/local/bin/npm
  Browsers:
    Chrome: 71.0.3578.98
    Firefox: Not Found
    Safari: 12.0
  npmGlobalPackages:
    @vue/cli: 3.2.1

Steps to reproduce

• yarn
• yarn build --modern

What is expected?

should generate two versions bundle, one for modern, and other for legacy.

What is actually happening?

only the legacy bundle be generated.

---

I think the problem is babel-loader using the cached babel.config.js. when building the modern version, it still use the legacy babel config, so the output bundle is same as legacy bundle.

the hash is same.

[haoqunjiang]

Thank you for your reporting! I should have seen this earlier…
Anyway, it was fixed in #3477