* Add --fallback to prevent problems with obsolete substitutes.

Dependencies

• [2] UMOJJ6DV time out to 3600 for now
• [3] G5A7TZVI * Don't discard old build steps when restarting a build.
• [4] CLJQCY2X * Store info about all the build actions and allow them to be
• [5] S3ZLZP3N * Cut off builds after half an hour of apparent inactivity. This
• [6] 7YBYT2LQ
• [7] A63IHCMX * Register GC roots properly.
• [8] BD3GRK4B * Get rid of "positive failures" and separate log phases.

Change contents

• replacement in src/script/hydra_build.pl at line 164
  [3.5001]→[2.0:87](∅→∅),[2.87]→[3.1033:1105](∅→∅),[3.87]→[3.1033:1105](∅→∅)
  − my $cmd = "nix-store --max-silent-time 3600 --keep-going --no-build-output " .

  − "--log-type flat --print-build-trace --realise $drvPath " .
  [3.5001]

  [3.1105]
  + my $cmd = "nix-store --realise $drvPath " .

  + "--max-silent-time 3600 --keep-going --fallback " .

  + "--no-build-output --log-type flat --print-build-trace " .