Build platform option

# Feature Request

## Motivation Behind Feature

I would like to run the windows build on my windows machine, and linux build on my linux.

## Feature Description

`cordova build electron --platform=windows` or similar should be nice

## Alternatives or Workarounds

Right now I achieve this by deleting parts of the json before running the build.

Start by tracing the Electron build command and how platform settings are read from the project JSON. Compare the requested `cordova build electron --platform=windows` behavior with the current manual JSON-editing workaround. Done means Windows and Linux builds can select the requested platform without deleting JSON settings first.

Written by the indexing model from the issue text.