in addition to c++ check also for g++ in the path, fixes ROOT-5706.
in addition to c++ check also for g++ in the path, fixes ROOT-5706.

agarciamontoro/root,buuck/root,arch1tect0r/root,omazapa/root-old,omazapa/root-old,sbinet/cxx-root,zzxuanyuan/root-compressor-dummy,evgeny-boger/root,BerserkerTroll/root,georgtroska/root,arch1tect0r/root,gganis/root,simonpf/root,bbockelm/root,olifre/root,0x0all/ROOT,gbitzes/root,karies/root,omazapa/root,nilqed/root,CristinaCristescu/root,pspe/root,lgiommi/root,krafczyk/root,esakellari/root,zzxuanyuan/root,perovic/root,veprbl/root,abhinavmoudgil95/root,esakellari/my_root_for_test,buuck/root,jrtomps/root,veprbl/root,jrtomps/root,dfunke/root,omazapa/root,bbockelm/root,simonpf/root,buuck/root,dfunke/root,georgtroska/root,zzxuanyuan/root-compressor-dummy,karies/root,gbitzes/root,mhuwiler/rootauto,esakellari/my_root_for_test,abhinavmoudgil95/root,perovic/root,pspe/root,arch1tect0r/root,vukasinmilosevic/root,smarinac/root,gganis/root,bbockelm/root,sawenzel/root,evgeny-boger/root,CristinaCristescu/root,omazapa/root-old,lgiommi/root,arch1tect0r/root,davidlt/root,mhuwiler/rootauto,Y--/root,satyarth934/root,sbinet/cxx-root,esakellari/root,sbinet/cxx-root,mattkretz/root,smarinac/root,perovic/root,mkret2/root,evgeny-boger/root,zzxuanyuan/root-compressor-dummy,BerserkerTroll/root,lgiommi/root,krafczyk/root,mkret2/root,root-mirror/root,dfunke/root,mkret2/root,smarinac/root,bbockelm/root,beniz/root,mkret2/root,mhuwiler/rootauto,davidlt/root,BerserkerTroll/root,thomaskeck/root,esakellari/my_root_for_test,veprbl/root,sbinet/cxx-root,smarinac/root,karies/root,satyarth934/root,Y--/root,agarciamontoro/root,mhuwiler/rootauto,0x0all/ROOT,beniz/root,gbitzes/root,georgtroska/root,davidlt/root,zzxuanyuan/root,olifre/root,gganis/root,davidlt/root,georgtroska/root,veprbl/root,veprbl/root,mhuwiler/rootauto,thomaskeck/root,mattkretz/root,arch1tect0r/root,nilqed/root,sbinet/cxx-root,beniz/root,gbitzes/root,sawenzel/root,lgiommi/root,gganis/root,karies/root,krafczyk/root,karies/root,abhinavmoudgil95/root,nilqed/root,davidlt/root,lgiommi/root,simonpf/root,krafczyk/root,simonpf/root,Duraznos/root,buuck/root,zzxuanyuan/root,evgeny-boger/root,agarciamontoro/root,gbitzes/root,mattkretz/root,evgeny-boger/root,evgeny-boger/root,jrtomps/root,sbinet/cxx-root,Y--/root,veprbl/root,beniz/root,zzxuanyuan/root,sirinath/root,Duraznos/root,gganis/root,davidlt/root,Duraznos/root,pspe/root,agarciamontoro/root,Duraznos/root,omazapa/root,georgtroska/root,gganis/root,georgtroska/root,sirinath/root,lgiommi/root,nilqed/root,jrtomps/root,agarciamontoro/root,CristinaCristescu/root,zzxuanyuan/root-compressor-dummy,mhuwiler/rootauto,olifre/root,esakellari/root,BerserkerTroll/root,BerserkerTroll/root,pspe/root,olifre/root,sawenzel/root,mkret2/root,abhinavmoudgil95/root,0x0all/ROOT,mattkretz/root,root-mirror/root,beniz/root,karies/root,dfunke/root,pspe/root,agarciamontoro/root,perovic/root,beniz/root,smarinac/root,krafczyk/root,gbitzes/root,buuck/root,beniz/root,lgiommi/root,gganis/root,sawenzel/root,CristinaCristescu/root,sawenzel/root,pspe/root,CristinaCristescu/root,vukasinmilosevic/root,Duraznos/root,nilqed/root,nilqed/root,lgiommi/root,lgiommi/root,esakellari/my_root_for_test,evgeny-boger/root,perovic/root,mkret2/root,omazapa/root,zzxuanyuan/root,mkret2/root,mhuwiler/rootauto,zzxuanyuan/root-compressor-dummy,jrtomps/root,olifre/root,bbockelm/root,karies/root,davidlt/root,sirinath/root,mattkretz/root,simonpf/root,BerserkerTroll/root,sawenzel/root,omazapa/root-old,thomaskeck/root,CristinaCristescu/root,omazapa/root,nilqed/root,mattkretz/root,veprbl/root,mhuwiler/rootauto,esakellari/root,0x0all/ROOT,Y--/root,CristinaCristescu/root,BerserkerTroll/root,omazapa/root-old,abhinavmoudgil95/root,karies/root,olifre/root,simonpf/root,buuck/root,omazapa/root-old,thomaskeck/root,krafczyk/root,thomaskeck/root,zzxuanyuan/root,BerserkerTroll/root,jrtomps/root,omazapa/root-old,simonpf/root,arch1tect0r/root,sawenzel/root,buuck/root,vukasinmilosevic/root,thomaskeck/root,jrtomps/root,mkret2/root,zzxuanyuan/root-compressor-dummy,root-mirror/root,smarinac/root,zzxuanyuan/root-compressor-dummy,bbockelm/root,sbinet/cxx-root,georgtroska/root,evgeny-boger/root,esakellari/root,agarciamontoro/root,Y--/root,sirinath/root,Duraznos/root,nilqed/root,omazapa/root-old,esakellari/my_root_for_test,agarciamontoro/root,sawenzel/root,agarciamontoro/root,bbockelm/root,BerserkerTroll/root,zzxuanyuan/root-compressor-dummy,sirinath/root,arch1tect0r/root,omazapa/root-old,mkret2/root,georgtroska/root,mattkretz/root,0x0all/ROOT,Duraznos/root,Y--/root,beniz/root,vukasinmilosevic/root,georgtroska/root,olifre/root,esakellari/my_root_for_test,esakellari/root,Y--/root,gganis/root,karies/root,root-mirror/root,omazapa/root,Duraznos/root,georgtroska/root,zzxuanyuan/root-compressor-dummy,Y--/root,evgeny-boger/root,davidlt/root,satyarth934/root,evgeny-boger/root,zzxuanyuan/root,davidlt/root,davidlt/root,dfunke/root,sirinath/root,dfunke/root,nilqed/root,gganis/root,smarinac/root,arch1tect0r/root,sbinet/cxx-root,mkret2/root,root-mirror/root,abhinavmoudgil95/root,omazapa/root,esakellari/root,sbinet/cxx-root,sirinath/root,vukasinmilosevic/root,dfunke/root,evgeny-boger/root,sbinet/cxx-root,zzxuanyuan/root,mattkretz/root,esakellari/root,smarinac/root,bbockelm/root,olifre/root,Duraznos/root,nilqed/root,olifre/root,esakellari/my_root_for_test,abhinavmoudgil95/root,gbitzes/root,vukasinmilosevic/root,karies/root,perovic/root,omazapa/root,thomaskeck/root,esakellari/my_root_for_test,pspe/root,0x0all/ROOT,vukasinmilosevic/root,pspe/root,perovic/root,dfunke/root,beniz/root,sbinet/cxx-root,esakellari/root,gbitzes/root,0x0all/ROOT,satyarth934/root,dfunke/root,BerserkerTroll/root,mattkretz/root,mhuwiler/rootauto,zzxuanyuan/root-compressor-dummy,omazapa/root-old,Y--/root,omazapa/root,agarciamontoro/root,krafczyk/root,satyarth934/root,satyarth934/root,zzxuanyuan/root,veprbl/root,BerserkerTroll/root,sirinath/root,gganis/root,abhinavmoudgil95/root,pspe/root,satyarth934/root,zzxuanyuan/root,abhinavmoudgil95/root,perovic/root,mattkretz/root,pspe/root,jrtomps/root,gbitzes/root,smarinac/root,vukasinmilosevic/root,root-mirror/root,veprbl/root,veprbl/root,lgiommi/root,esakellari/root,gbitzes/root,sirinath/root,root-mirror/root,omazapa/root,gbitzes/root,dfunke/root,simonpf/root,nilqed/root,omazapa/root-old,pspe/root,esakellari/my_root_for_test,vukasinmilosevic/root,CristinaCristescu/root,CristinaCristescu/root,Duraznos/root,mattkretz/root,zzxuanyuan/root,0x0all/ROOT,arch1tect0r/root,georgtroska/root,satyarth934/root,beniz/root,arch1tect0r/root,sawenzel/root,perovic/root,thomaskeck/root,mkret2/root,jrtomps/root,dfunke/root,bbockelm/root,Duraznos/root,vukasinmilosevic/root,omazapa/root,vukasinmilosevic/root,root-mirror/root,bbockelm/root,esakellari/root,jrtomps/root,krafczyk/root,CristinaCristescu/root,karies/root,root-mirror/root,sirinath/root,simonpf/root,root-mirror/root,zzxuanyuan/root,krafczyk/root,olifre/root,lgiommi/root,smarinac/root,thomaskeck/root,perovic/root,olifre/root,buuck/root,sawenzel/root,simonpf/root,satyarth934/root,bbockelm/root,0x0all/ROOT,perovic/root,buuck/root,krafczyk/root,abhinavmoudgil95/root,beniz/root,abhinavmoudgil95/root,agarciamontoro/root,esakellari/my_root_for_test,mhuwiler/rootauto,Y--/root,buuck/root,Y--/root,mhuwiler/rootauto,krafczyk/root,zzxuanyuan/root-compressor-dummy,gganis/root,veprbl/root,sawenzel/root,satyarth934/root,sirinath/root,satyarth934/root,thomaskeck/root,simonpf/root,root-mirror/root,arch1tect0r/root,davidlt/root,buuck/root,CristinaCristescu/root,jrtomps/root