Fix build

Dependencies

• [2] SYN2GC3O allow null values for jobs, meaning it should build
• [3] 4LWGZL33
• [4] AEKIREIH * Updated hydra_eval_jobs for the new evaluator.
• [*] 4N5APGRG * Start of a helper tool to evaluate job expressions efficiently.

Change contents

• edit in src/c/hydra-eval-jobs.cc at line 194
  [3.2048]

  [3.2048]
  + Bindings & tmp(*state.allocBindings(0));
• replacement in src/c/hydra-eval-jobs.cc at line 198
  [3.2214]→[3.2214:2239](∅→∅)
  − Bindings());
  [3.2214]

  [2.0]
  + tmp);