title: Can't use mkdir in NPM script from Windows
body: <p>I'm trying to have a script that looks like this:</p>
  
  <pre><code>{
      "scripts":
          "setup": "mkdir -p ./my-dir"
  }
  </code></pre>
  
  <p>And it fails, at least on Windows, even if I run it from a Git Bash prompt. Even trying just <code>mkdir ./my-dir</code> doesn't work. I can't figure out any reason it should fail.</p>
  
  <p>The error it gives is a "syntax incorrect" error:</p>
  
  <pre><code>&gt; my-app@0.0.1 stage C:\my-app
  &gt; mkdir ./my-dir
  
  The syntax of the command is incorrect.
  
  npm ERR! Windows_NT 6.1.7601
  npm ERR! argv "C:\\Program Files\\nodejs\\node.exe" "C:\\Program Files\\nodejs\\node_modules\\npm\\bin\\npm-cli.js" "run" "stage"
  npm ERR! node v6.4.0
  npm ERR! npm  v3.10.3
  npm ERR! code ELIFECYCLE
  npm ERR! my-app@0.0.1 stage: `mkdir ./my-dir`
  npm ERR! Exit status 1
  npm ERR!
  npm ERR! Failed at the my-app@0.0.1 stage script 'mkdir ./my-dir'.
  npm ERR! Make sure you have the latest version of node.js and npm installed.
  npm ERR! If you do, this is most likely a problem with the my-app package,
  npm ERR! not with npm itself.
  npm ERR! Tell the author that this fails on your system:
  npm ERR!     mkdir ./my-dir
  npm ERR! You can get information on how to open an issue for this project with:
  npm ERR!     npm bugs my-app
  npm ERR! Or if that isn't available, you can get their info via:
  npm ERR!     npm owner ls my-app
  npm ERR! There is likely additional logging output above.
  
  npm ERR! Please include the following file with any support request:
  npm ERR!     C:\my-app\npm-debug.log
  </code></pre>
  
  <p>If this won't work, is there a cross-platform friendly way to initialize an empty directory?</p>