Don't copy src for nix-shell

Dependencies

• [2] FV2M6MOT hydra: use autoconf/-make
• [3] QK2OXCKP hydra/release.nix: move manual to tarball build, restore version in store path for tarball build
• [4] UHMUHQMU hydra: fix tarball build, add pre suffix to tarballs
• [*] T4LLYESZ * Nix expression for building Hydra.

Change contents

• replacement in release.nix at line 35
  [2.17676]→[2.17676:17698](∅→∅)
  − src = hydraSrc;
  [2.17653]

  [2.17698]
  + src = if lib.inNixShell then null else hydraSrc;