Use a better* solution for the missing CMD file issue on Windows

[BYK]

This is a follow up to #3806. Instead of recreating the file and
leaving it there, we trick CMD to stop reading the file after the
first line by modifying the CMD script.

*This is a "better" solution because:

1. It doesn't leave obsolete files around
2. This fix can be incorporated into npm and yarn via https://github.com/npm/cmd-shim/

[gaearon]

Looks like Windows still fails :-(

The batch file cannot be found.
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! [email protected] eject: `react-scripts eject`

[BYK]

Ah, of course, because I cannot rewrite a file that's being run at the time 😞

I'll reopen this when I figure it out.