Fix CMake error with stand-alone cling
Fix CMake error with stand-alone cling

Use absolute PATH when checking the existance of the textinput directory. This prevent this error:

CMake Error at cmake/modules/AddLLVM.cmake:312 (add_library):
  Cannot find source file:

    C:/build/workspace/cling-test/src/core/textinput/src/textinput/Editor.cpp

  Tried extensions .c .C .c++ .cc .cpp .cxx .m .M .mm .h .hh .h++ .hm .hpp
  .hxx .in .txx
Call Stack (most recent call first):
  tools/cling/CMakeLists.txt:142 (llvm_add_library)
  tools/cling/lib/UserInterface/CMakeLists.txt:17 (add_cling_library)

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