hydra-eval-jobs: Reinitialize Boehm GC in the child

Dependencies

• [2] 5MP35ORV hydra-eval-jobs: Ugly hackery to reduce memory usage
• [*] 4N5APGRG * Start of a helper tool to evaluate job expressions efficiently.
• [*] M3A5PZIH hydra: Clarify the dependency on BDW-GC.
• [*] 3PNG7NIB Remove trailing whitespace

Change contents

• edit in src/hydra-eval-jobs/hydra-eval-jobs.cc at line 4
  [5.355]

  [5.355]
  + #define GC_LINUX_THREADS 1
• edit in src/hydra-eval-jobs/hydra-eval-jobs.cc at line 268
  [2.2450]

  [6.808]
  +

  + GC_atfork_prepare();
• edit in src/hydra-eval-jobs/hydra-eval-jobs.cc at line 273
  [2.2531]

  [6.810]
  +

  + GC_atfork_child();

  + GC_start_mark_threads();
• edit in src/hydra-eval-jobs/hydra-eval-jobs.cc at line 308
  [2.3692]

  [2.3692]
  +

  + GC_atfork_parent();