mk-aggregated: prepend rpath instead of setting it

The original binary may have outstanding RPATH, eg. to libgcc_s, which
must be kept.

lib/mk-aggregated.nix

@@ -47,7 +47,9 @@ symlinkJoin {
  [[ $file != */*clippy* ]] || cp --remove-destination "$(realpath -e $file)" $file
  chmod +w $file
  ${lib.optionalString stdenv.isLinux ''
- patchelf --set-rpath $out/lib "$file" || true
+ if prev_rpath="$(patchelf --print-rpath "$file")"; then
+ patchelf --set-rpath "$out/lib''${prev_rpath:+:}$prev_rpath" "$file"
+ fi
  ''}
  ${lib.optionalString stdenv.isDarwin ''
  install_name_tool -add_rpath $out/lib "$file" || true