The Node documentation for `exec` states:
> Never pass unsanitized user input to this function. Any input containing shell metacharacters may be used to trigger arbitrary command execution.
The `outputPath`, `options.buildTarget` and `options.maxParallel` come from `nx.json`. Careful crafting of these fields can result in NX executing arbitrary commands.
This patch fixes this by using `execFile`, which does not spawn a shell.
