* libclang_rt-san-* is sanitizer_common, and is linked in only if no other
sanitizer runtime is present.
* libclang_rt-ubsan-* is the piece of the runtime which doesn't depend on
a C++ ABI library, and is always linked in.
* libclang_rt-ubsan_cxx-* is the piece of the runtime which depends on a
C++ ABI library, and is only linked in when linking a C++ binary.
The Darwin ubsan runtime is unchanged.
For more details, see Clang change r177605.
llvm-svn: 177606