How do I build the Rhino specific versions of less

Question

I want to run the latest version of less from Java, for this (I believe) I need the Rhino specific versions of less. From the less website:

Each less.js release contains also rhino-compatible version.

But this appears to have been not the case since v1.7.5.

So I've installed NPM, installed Grunt, downloaded the less source from GitHub, ran grunt -help to find the rhino task but have fallen at the last hurdle:

C:\Temp\less.js-2.5.0> grunt rhino

Running "browserify:rhino" (browserify) task
Verifying property browserify.rhino exists in config...ERROR
>> Unable to process task.
Warning: Required config property "browserify.rhino" missing. Use --force to continue.

Aborted due to warnings.

Forcing doesn't help (produces an empty lessc-rhino.js file) - any ideas as to what I'm missing?