`cordova build` does not regenerate `platforms` directories

If the `platforms` directory is deleted from a Cordova project, running `cordova build` fails to restore it from the `config.xml` file, as it should, and instead gives the error message:

Error: No platforms added to this project. Please use `cordova platform add <platform>`.

Running `cordova prepare` does however correctly restore it. However, since the documentation for `cordova build` clearly indicates that it is equivalent to running `cordova prepare` + `cordova compile`, this should not be the case.

Note: `cordova build` is able to restore the `plugins` directory without any problems.