native_cctools: Don't use libc++ from pinned clang
native_cctools: Don't use libc++ from pinned clang

Now that we include the macOS SDK libc++ headers in our macOS SDK
tarball, we no longer need this hack to use the libc++ from our pinned
clang.


Former-commit-id: c72bc78e1c2e5fa2f554db4ca645d9f716940808
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin