Version 9.3.2 breaks my zeit.co build

Bug report

Last hotfix version breaks the zeit.co build.

Describe the bug

Update to next.js version 9.3.2 and try to deploy your application via zeit.co. The next build step fails with:

 Automatically optimizing pages...
 > Build error occurred
  _error_Error {
  props: "Cannot find module 'private-next-pages/index.spec.tsx'",
    context: undefined,
   refs: {},
 updater: {
    isMounted: [Function: isMounted],
    enqueueForceUpdate: [Function: enqueueForceUpdate],
   enqueueReplaceState: [Function: enqueueReplaceState],
   enqueueSetState: [Function: enqueueSetState]
  },
    code: 'MODULE_NOT_FOUND'
 }
...

To Reproduce

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

1. Setup a typescript based nextjs project
2. Setup deployment in zeit.co
3. Start deployment
4. See error

Expected behavior

It should just work as before. After downgrade, it works again.

[hrasekj]

This error breaks also examples. I just copied blog-starter. Run npm install then npm run build and got this error:

Creating an optimized production build ..fs.js:885
  return binding.mkdir(pathModule._makeLong(path),
                 ^

Error: EEXIST: file already exists, mkdir '/home/polonium/www/cyclone/blog-starter/.next/cache/next-minifier'
    at fs.mkdirSync (fs.js:885:18)
    at new TaskRunner (/home/polonium/www/cyclone/blog-starter/node_modules/next/dist/build/webpack/plugins/terser-webpack-plugin/src/TaskRunner.js:1:634)
    at TerserPlugin.optimizeFn (/home/polonium/www/cyclone/blog-starter/node_modules/next/dist/build/webpack/plugins/terser-webpack-plugin/src/index.js:6:1316)
    at AsyncSeriesHook.eval [as callAsync] (eval at create (/home/polonium/www/cyclone/blog-starter/node_modules/tapable/lib/HookCodeFactory.js:33:10), <anonymous>:21:1)
    at AsyncSeriesHook.lazyCompileHook (/home/polonium/www/cyclone/blog-starter/node_modules/tapable/lib/Hook.js:154:20)
    at hooks.additionalAssets.callAsync.err (/home/polonium/www/cyclone/blog-starter/node_modules/webpack/lib/Compilation.js:1409:36)
    at AsyncSeriesHook.eval [as callAsync] (eval at create (/home/polonium/www/cyclone/blog-starter/node_modules/tapable/lib/HookCodeFactory.js:33:10), <anonymous>:6:1)
    at AsyncSeriesHook.lazyCompileHook (/home/polonium/www/cyclone/blog-starter/node_modules/tapable/lib/Hook.js:154:20)
    at hooks.optimizeTree.callAsync.err (/home/polonium/www/cyclone/blog-starter/node_modules/webpack/lib/Compilation.js:1405:32)
    at AsyncSeriesHook.eval [as callAsync] (eval at create (/home/polonium/www/cyclone/blog-starter/node_modules/tapable/lib/HookCodeFactory.js:33:10), <anonymous>:6:1)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! blog-starter@1.0.0 build: `next build`
npm ERR! Exit status 1

[balazsorban44]

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