This prints NO if LLVM was built with -fno-rtti or an equivalent flag
and YES otherwise. The reasons to add -has-rtti rather than adding -fno-rtti
to --cxxflags are:
- Building LLVM with -fno-rtti does not always mean that client
applications need this flag.
- Some compilers have a different flag for disabling rtti, and the
compiler being used to build LLVM may not be the compiler being used to
build the application.