added llvm code coverage file to gitignore
added llvm code coverage file to gitignore

Antondomashnev/Sourcery,Antondomashnev/Sourcery,krzysztofzablocki/Sourcery,krzysztofzablocki/Sourcery,Antondomashnev/Sourcery,Antondomashnev/Sourcery,Antondomashnev/Sourcery,krzysztofzablocki/Sourcery,krzysztofzablocki/Sourcery