this commit implements a more reliable way of setting the CLI's exit code in error cases.

Previously, I encountered this error when running the cli:
```console
$ cordova build
TypeError [ERR_INVALID_ARG_TYPE]: The "code" argument must be of type number. Received type string ('ERR_UNHANDLED_ERROR')
    at process.set [as exitCode] (node:internal/bootstrap/node:123:9)
    at /opt/nodejs/lib/node_modules/cordova/bin/cordova:33:22
```

With this version, I get to see the root problem:
```console
$ cordova build
Unhandled error. ('Parsing /home/me/hello/config.xml failed')
```