ikvmc -target:library groovy-all-1.1-SNAPSHOT5.0.jar
However, some errors warning will appear, but you can ignore them. After compilation you should have groovy-all-1.1-SNAPSHOT5.0.dll in the current directory.
in the interactive console (the binary in the attachment of this page).
On some machines, there will be a test encoding issue to stop Groovy compiling script files. This seems to be the use of different encoding names between Java and .NET. If you find this kind of error, try specifying "-c" when testing with groovy.ui.GroovyMain class.
Further development as a Groovy module?