only run extension standalone specs on 2.4+
only run extension standalone specs on 2.4+

The separate extensions directory was introduced in RubyGems 2.4.
joshsoftware/bundler,christer155/bundler,ipmobiletech/bundler,gregkare/bundler,simplybusiness/bundler,elovelan/bundler,seanlinsley/bundler,chef/bundler,h4ck3rm1k3/bundler,tgxworld/bundler,ximus/bundler,h4ck3rm1k3/bundler,mvz/bundler,chulkilee/bundler,pivotal-cf-experimental/bundler,philnash/bundler,kohgpat/bundler,masarakki/bundler,mpapis/bundler,anil826/bundler,philnash/bundler,Wirachmat/bundler,ipmobiletech/bundler,joshsoftware/bundler,schaary/bundler,robinboening/bundler,bundler/bundler,anil826/bundler,Eric-Guo/bundler,gregkare/bundler,bronzdoc/bundler,christer155/bundler,bronzdoc/bundler,dilumnavanjana/bundler,agis-/bundler,pivotal-cf-experimental/bundler,robinboening/bundler,masarakki/bundler,danimashu/bundler,carpodaster/bundler,zhangkuaiji/bundler,chef/bundler,seanlinsley/bundler,Wirachmat/bundler,jingweno/bundler,Eric-Guo/bundler,asutoshpalai/bundler,asutoshpalai/bundler,mvz/bundler,suhastech/bundler,schaary/bundler,mpapis/bundler,zhangkuaiji/bundler,lmtim/bundler,dilumnavanjana/bundler,cdwort/bundler,jasonkarns/bundler,RochesterinNYC/bundler,danimashu/bundler,jingweno/bundler,elovelan/bundler,simplybusiness/bundler,chulkilee/bundler,Teino1978-Corp/Teino1978-Corp-bundler,neslom/bundler,agis-/bundler,Teino1978-Corp/Teino1978-Corp-bundler,davydovanton/bundler,AiyionPrime/bundler,neslom/bundler,davydovanton/bundler,suhastech/bundler,RochesterinNYC/bundler,kohgpat/bundler,cdwort/bundler,jasonkarns/bundler,bundler/bundler,lmtim/bundler,AiyionPrime/bundler,ximus/bundler,carpodaster/bundler,tgxworld/bundler