I did not go through the full thread but it seems that you are trying to avoid the GNU runtimes for your system toolchain by using LLVM.
Bootstrapping LLVM without external libc is currently not possible as the libc project is at a very early stage. We do not have loaders and many symbols are still missing.
If you want to bootstrap LLVM without GNU, I guess it is possible. For example, one can first try to put up a sysroot with busybox and musl and then build things upon that sysroot. In your case, I think you already have the LFS.