Ability to set run options/diagnostics in schemes

If this is something currently supported, let me know and I can make it more clear in the docs.

The "run" options in a scheme have several options that are unable to be set via XcodeGen. Namely those in the "Options" and "Diagnostics" tabs:

Setting one of these options results in fairly irregular output in the resulting xcscheme file. This example shows what is generated for enabling the thread sanitizer and zombies:

It would be great to have first-class support for these fields in YAML. i.e.:

run:
  enableThreadSanitizer: true
  commandLineArguments:
    "-set-store": false
   ... etc