Rhino version does not create source map file

This is related to #2043. I used command:

java -jar js.jar -f less-rhino-1.7.0.js lessc-rhino-1.7.0.js --source-map less.less less.css

This is how less.less looks like:

.test {
  demo: value;
}

Source map file was not created.

Note 1: The --source-map option is not ignored by rhino, because following:

java -jar js.jar -f less-rhino-1.7.0.js lessc-rhino-1.7.0.js --source-map less.less

returns expected error:

output: undefined
the sourcemap option only has an optional filename if the css filename is given

Note 2: the same file compiled under node.js generated source map file:

{"version":3,"file":"less.css","sources":["less.less"],"names":[],"mappings":"AAAA;EACE,WAAA"}

Start by running the reported Rhino command with less-rhino-1.7.0.js, lessc-rhino-1.7.0.js, and less.less, then compare it with the Node.js result. Trace the Rhino command-line handling of --source-map and less.css. Done means the Rhino invocation creates a source map for less.less and less.css like the Node.js invocation.