yarn deploy fails to build a mirror-saga dependencies #4170

Environment

1. node -v: 9,3,0
2. npm -v: 5.5.1
3. yarn --version (if you use Yarn): 1.5.1
4. yarn list react-scripts (if you haven’t ejected): 1.1.1

Then, specify:

1. Operating system: Linux Version 3.16.0-5-amd64, Compiled Add missing semver dependency #1 SMP Debian 3.16.51-3+deb8u1 (2018-01-08)
2. Browser and version (if relevant): Google Chrome Version 65.0.3325.162 (Official Build) (64-bit)

Steps to Reproduce

I'm using a mirror-saga to build a redux-saga and firebase hosting to my React project.
More details here: https://github.com/ShMcK/mirror-saga

1. I'm trying to build a project using yarn and react-app-env
2. Failed to minify the code from this file:
3. I try to use `@babel/preset-env to fix it
4. I write a .baberc file but didn't work.

Expected Behavior

Compile my mirror-saga dependencies correctly.

Actual Behavior

$ firebase use default && react-app-env --env-file=.env.prod build
Now using alias default (opevere-game)
Creating an optimized production build...
Failed to compile.

Failed to minify the code from this file: 

 	./node_modules/mirror-saga/src/index.js:4:28 

Read more here: http://bit.ly/2tRViJ9

Done in 18.24s.

.babelrc file:

{
    "presets": [
        ["@babel/preset-env", {
            "targets": {
                "esmodules": true,
                "browsers": ["last 2 versions", "safari >= 7"]
            }
        }]
    ]
}

error output:

$ head -n 10 ./node_modules/mirror-saga/src/index.js 
import sagaMiddleware from './middleware'
import addEffect from './effects'

export default (options = {}) => {
  const middlewares = options.middlewares || []
  // overwrite defaults
  return Object.assign(options, {
    middlewares: middlewares.concat([sagaMiddleware]),
    addEffect,
  })