Disable automatic download for Groovy grapes

A sample script ss.groovy:

@Grab(group='org.codehaus.groovy.modules.http-builder', 
      module='http-builder', 
      version='0.5.0')
import groovyx.net.http.HTTPBuilder

println('done')

for some reason takes ~25 seconds to load when run with

groovy ss.groovy

and ~5 seconds when run with

groovy -Dgroovy.grape.autoDownload=false ss.groovy

as per this StackOverflow explanation. I tried doing manual initialization with

Grape.enableAutoDownload = false
Grape.grab(group:'org.codehaus.groovy.modules.http-builder', 
           module:'http-builder',
           version:'0.5.0')
import groovyx.net.http.HTTPBuilder
println('done')

but this fails on import with:

/tmp/ss.groovy: 3: unable to resolve class groovyx.net.http.HTTPBuilder
 @ line 3, column 1.
  import groovyx.net.http.HTTPBuilder
  ^

Is there a contained way to either:

• Make it not download the artifacts automatically (preferred, as it allows for solving other issues, e.g. external site down while an artifact already exists in the local cache)
• Make it startup faster in any other way

By contained I mean that all additional instructions should be either within script or, if no such one exists, an acceptable default (e.g. don't check the cached artifacts for updates - I would still, however, like to have automatic downloads globally) to be put in some of groovy config files (e.g. ~/.groovy/grapeConfig.xml or similar).

Update: The issue has been fixed, @GrabConfig(autoDownload=false) will be available in Groovy 2.2