Next with-firebase-hosting example doesn't seem to work.

Bug report

Describe the bug

I’ve just tried testing the zwith-firebase-hosting[example](https://github.com/zeit/next.js/tree/canary/examples/with-firebase-hosting) and thenpm run devruns ok, but when i trynpm run serve` it fails with this error:

Build error occurred { Error: EEXIST: file already exists, mkdir ‘/Users/user/Sites/with-firebase-hosting/dist/functions/next’ errno: -17, code: ‘EEXIST’, syscall: ‘mkdir’, path: ‘/Users/user/Sites/with-firebase-hosting/dist/functions/next’ } npm ERR! errno 1 npm ERR! with-firebase-hosting@4.0.1 build-app: next build "src/app/" npm ERR! Exit status 1 npm ERR! npm ERR! Failed at the with-firebase-hosting@4.0.1 build-app script.

To Reproduce

Follow the steps in the with-firebase-hosting example

Expected behavior

The application to run according to the readme file.

System information

• OS: MAC Os Catalina
• Browser (if applies) [e.g. chrome, safari]
• Version of Next.js: latest
• Version of NodeJS: v8.15.0 (required by firebase functions)

[ShayDavidson]

@jenyayel We were on Node 10.11. When I upgraded to 10.12 it started working (as mentioned in this thread https://stackoverflow.com/questions/13696148/node-js-create-folder-or-use-existing/24311711)

[ShayDavidson]

got a similar error when i use my docker setup. previously on 9.1.2 it didn’t happen. upgraded to 9.3.2 and the error occurs:

next build

Creating an optimized production build...

> Build error occurred
{ [Error: EEXIST: file already exists, mkdir '/app/.next']
  errno: -17,
  code: 'EEXIST',
  syscall: 'mkdir',
  path: '/app/.next' }