I have a dojo build profile that builds two layers- one layer dojo/dojo layer and another layer for my app files. In version 1.5 to build the dojo, basically for bare utilities for browser detection, these js files are required.
load(buildscriptsPath + "../../dojo/_base/_loader/bootstrap.js");
load(buildscriptsPath + "../../dojo/_base/_loader/loader.js");
load(buildscriptsPath + "../../dojo/_base/_loader/hostenv_rhino.js");
now with version 1.7, they have removed these files and there is not any reference on buildUtil.js