cpp.kak: fix alt_dirs handling with more than 2 directories
cpp.kak: fix alt_dirs handling with more than 2 directories

elegios/kakoune,xificurC/kakoune,zakgreant/kakoune,jjthrash/kakoune,Asenar/kakoune,xificurC/kakoune,alpha123/kakoune,rstacruz/kakoune,lenormf/kakoune,zakgreant/kakoune,ekie/kakoune,jjthrash/kakoune,danr/kakoune,danr/kakoune,ekie/kakoune,mawww/kakoune,mawww/kakoune,Somasis/kakoune,occivink/kakoune,zakgreant/kakoune,elegios/kakoune,danr/kakoune,alpha123/kakoune,alexherbo2/kakoune,alexherbo2/kakoune,mawww/kakoune,jkonecny12/kakoune,ekie/kakoune,jkonecny12/kakoune,flavius/kakoune,jkonecny12/kakoune,Somasis/kakoune,casimir/kakoune,casimir/kakoune,danielma/kakoune,jjthrash/kakoune,xificurC/kakoune,casimir/kakoune,rstacruz/kakoune,danielma/kakoune,Somasis/kakoune,occivink/kakoune,flavius/kakoune,zakgreant/kakoune,jkonecny12/kakoune,alexherbo2/kakoune,alpha123/kakoune,danielma/kakoune,Asenar/kakoune,mawww/kakoune,elegios/kakoune,alexherbo2/kakoune,Asenar/kakoune,rstacruz/kakoune,casimir/kakoune,lenormf/kakoune,occivink/kakoune,ekie/kakoune,occivink/kakoune,elegios/kakoune,flavius/kakoune,lenormf/kakoune,xificurC/kakoune,jjthrash/kakoune,alpha123/kakoune,flavius/kakoune,danielma/kakoune,Somasis/kakoune,danr/kakoune,rstacruz/kakoune,Asenar/kakoune,lenormf/kakoune