hydra-queue-runner: Set isCachedBuild

Dependencies

• [2] 5AIYUMTB Basic remote building
• [3] ENXUSMSV Make concurrency more robust
• [4] 24BMQDZA Start of single-process hydra-queue-runner

Change contents

• replacement in src/hydra-queue-runner/hydra-queue-runner.cc at line 1141
  [3.9047]→[2.13956:14052](∅→∅)
  − markSucceededBuild(txn, build2, res, false, result.startTime, result.stopTime);
  [3.9047]

  [3.16587]
  + markSucceededBuild(txn, build2, res, build != build2,

  + result.startTime, result.stopTime);