There are repositories for maintenance of LLVM for the Hurd's needs:
grubber:~tschwinge/tmp/llvm/git, grubber:~tschwinge/tmp/llvm/clang/git,
grubber:~tschwinge/tmp/llvm/compiler-rt/git,
grubber:~tschwinge/tmp/llvm/test-suite/git.
These repositories are based on the upstream Git mirror repositories.