E.g. local file is Build/target/web/result.txt
Upload to gs://my-cloud
The filename in the cloud is "Build\target\web\result.txt"
The desired filename in the cloud is "result.txt"
Another plugin which handles this is the Flexible Publish plugin which has an additional field 'remove prefix' which will be removed prior to upload, so we could specify "Build/target/web" in this field to get the desired behaviour.
Please also note that ideally the path folder separator would be platform independent. I.e. we specify "Build/target/web" and this will work on Windows and Linux based slaves.