make sure compiler specified in ./configure is used. Fixes ROOT-5818.
make sure compiler specified in ./configure is used. Fixes ROOT-5818.

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