[compiler-rt] Link atomic against builtins (#65239)

The atomic shared library needs to be linked against builtins. The
`add_compiler_rt_runtime` call already has `DEP builtins` but that only
ensures that the `builtins` target is built before `clang_rt.atomic` but
doesn't link against `clang_rt.builtins`, to do so we need to use
`LINK_LIBS clang_rt.builtins`.