hydra-queue-runner: Fix assertion failure

Dependencies

• [2] LVQXQIYA Kill active build steps when builds are cancelled
• [3] EYR3EW6J Keep stats for the Hydra auto scaler
• [4] MHVIT4JY Split hydra-queue-runner.cc more
• [5] KQ3EGUQY Add some instrumentation to keep track of dispatcher cost
• [6] B2L4T3X6 Sync with Nix
• [7] TTBLPQAJ Keep track of wait time per system type
• [*] HJOEIMLR Refactor

Change contents

• replacement in src/hydra-queue-runner/builder.cc at line 16
  [2.1]→[2.1:45](∅→∅)
  − reservation->threadId = pthread_self();
  [2.1]

  [3.350]
  + auto activeStep = std::make_shared<ActiveStep>();

  + activeStep->step = reservation->step;

  + activeStep->threadId = pthread_self();

  + activeSteps_.lock()->insert(activeStep);
• edit in src/hydra-queue-runner/builder.cc at line 21
  [3.351]→[2.46:93](∅→∅)
  − activeSteps_.lock()->insert(reservation);

  −
• replacement in src/hydra-queue-runner/builder.cc at line 22
  [2.130]→[2.130:215](∅→∅)
  − reservation->threadId = -1;

  − activeSteps_.lock()->erase(reservation);
  [2.130]

  [2.215]
  + activeStep->threadId = -1;

  + activeSteps_.lock()->erase(activeStep);
• edit in src/hydra-queue-runner/state.hh at line 373
  [3.2908]→[2.4782:4846](∅→∅)
  − pthread_t threadId = 0;

  − bool cancelled = false;
• replacement in src/hydra-queue-runner/state.hh at line 377
  [2.4848]→[2.4848:4923](∅→∅)
  − nix::Sync<std::set<std::shared_ptr<MachineReservation>>> activeSteps_;
  [2.4848]

  [3.1480]
  + struct ActiveStep

  + {

  + Step::ptr step;

  + pthread_t threadId;

  + };
• edit in src/hydra-queue-runner/state.hh at line 383
  [3.1481]

  [3.1481]
  + nix::Sync<std::set<std::shared_ptr<ActiveStep>>> activeSteps_;

  +