config.build_dir is ignored for xcworkspace in Xcode4.4

[matzew]

Having a CocoaPods based project (https://github.com/aerogear/aerogear-ios) and did use the following Rakefile to build it:

    require 'rubygems'
require 'betabuilder'

BetaBuilder::Tasks.new do |config|
  # your Xcode target name
  config.target = "AeroGear-iOS"
  config.configuration = "Release" 
  config.build_dir = "buildDir"

  # the Xcode configuration profile
  config.workspace_path = "AeroGear-iOS.xcworkspace"
  config.scheme         = "AeroGear-iOS"
  ##config.app_name       = "MyApp"

end

But it looks like the build_dir is ignored...

...
BUILD:OUTPUT....
...
/bin/sh -c /Users/wessi/Library/Developer/Xcode/DerivedData/
...
** BUILD SUCCEEDED **

It is using the build location from 'File->Workspace Settings..' entry