clang-install now cooks host:llvm21 (which carries AMDGPU;NVPTX). rsync its
host LLVM (llvm-config + libs + llvm headers) into ~/.redoxer/toolchain so the
host llvm-config the Mesa build reads reports the amdgpu module (mesa's
dependency('llvm', modules: amdgpu) otherwise fails against the toolchain's
downloaded X86-only LLVM). Mirrors the existing relibc->toolchain propagation;
rsync without --delete preserves the toolchain's gcc/rust/redox-target files.
vasilito
448800aea9