Add a dict RUBYCOCOA_BUILD_CONFIG into Info.plist

the dict shows build environment of RubyCocoa.framework.

+ RUBYCOCOA_BUILD_CONFIG
  + MACOSX_DEPLOYMENT_TARGET
  + RUBY_VERSION

git-svn-id: https://svn.code.sf.net/p/rubycocoa/svn/trunk/src@2593 f4f36d40-9719-0410-9868-dde021a23eda