polyfills.map is injected when using next-source-maps

[tracy-liucui]

Bug report

Describe the bug

In this pull request(#9168), there is a new entry polyfills is added, but it also injected the polyfills.map when using next-source-maps.

To Reproduce

Steps to reproduce the behavior, please provide code snippets or a repository:

1. install [email protected]
2. use withSourceMaps in next config
3. check the source code of any page

Expected behavior

Only runtime/polyfills.js is included

Screenshots

System information

• OS: macOS
• Browser (if applies) chrome
• Version of Next.js: 9.1.4

Additional context

I think it is introduced from these lines (https://github.com/zeit/next.js/pull/9168/files#diff-038a496f54bcbe216b7304af084328cfR599-R617)

[balazsorban44]

This issue has been automatically locked due to no recent activity. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.