Remove signing parameter (nix#f435f82)

Dependencies

• [2] BYVRA54Q Temporarily disable machines on any exception, not just connection failures
• [3] NAYQT2GT hydra-queue-runner: Use cmdBuildDerivation
• [4] 73YR46NJ hydra-queue-runner: Write directly to a binary cache
• [5] DKJFD6JN Process Nix API changes
• [6] UVNTWTWG Prevent download of NARs we just uploaded
• [7] FITVNQ2S Keep track of the time we spend copying to/from build machines
• [8] 6TY4LNHH Finish copyClosure
• [*] 5AIYUMTB Basic remote building

Change contents

• replacement in src/hydra-queue-runner/build-remote.cc at line 109
  [3.91]→[3.339:387](∅→∅)
  − destStore->exportPaths(missing, false, to);
  [3.91]

  [3.365]
  + destStore->exportPaths(missing, to);
• replacement in src/hydra-queue-runner/build-remote.cc at line 363
  [2.8870]→[2.8870:8936](∅→∅)
  − destStore->importPaths(false, from, result.accessor);
  [2.8870]

  [3.231]
  + destStore->importPaths(from, result.accessor);