Version 5.1.2 broken on Node 4

[adamgruber]

• cross-env version: 5.1.2
• node version: 4.8.7
• npm (or yarn) version: 2.15.11

What you did:

• Ran npm script: cross-env NODE_ENV=test nyc mocha "test/spec/**/*.test.+(js|jsx)"

What happened:

• Threw an error: TypeError: Cannot supply flags when constructing one RegExp from another

Problem description:

• Offending line of code:

  cross-env/src/index.js

  Line 60 in 7fa5c08

  const re = new RegExp(/(\\)?'|([\\])(?=[$"\\])/, 'g')