bindings: get RUBY_VERSION
bindings: get RUBY_VERSION

Not all cmake versions get this variable right. So better retrieve it
here.

kkaempf/openwsman,vcrhonek/openwsman,kkaempf/openwsman,kolbma/openwsman,kkaempf/openwsman,Openwsman/openwsman,kkaempf/openwsman,kolbma/openwsman,vcrhonek/openwsman,vcrhonek/openwsman,Openwsman/openwsman,vcrhonek/openwsman,vcrhonek/openwsman,kolbma/openwsman,kolbma/openwsman,vcrhonek/openwsman,kkaempf/openwsman,kkaempf/openwsman,kolbma/openwsman,Openwsman/openwsman,kolbma/openwsman,Openwsman/openwsman,vcrhonek/openwsman,Openwsman/openwsman,kkaempf/openwsman,kolbma/openwsman,Openwsman/openwsman,Openwsman/openwsman