Our custom sbt updateEclipseClassifiers command requires that a user setup the DAFFODIL_HOME environment variable correctly. But this environment variable is actualy no longer needed in eclipse. It is only needed for this one sbt command.
To simplify eclipse setup, instead of getting the Daffodil directory from this environment variable, we should instead UpdateEclipseClassifers main() function accept the Daffodil directory as the first argument. This way, when run via sbt, sbt can pass in baseDirectory.value, and we can rid of this DAFFODIL_HOME step in the setup.