hydra-queue-runner: Use cmdBuildDerivation

See https://github.com/NixOS/nix/commit/1511aa9f488ba0762c2da0bf8ab61b5fde47305d and https://github.com/NixOS/nix/commit/eda2f36c2ac847e02e871c327e7633693d92cd8d.

Created by  Eelco Dolstra  on July 20, 2015
NAYQT2GTCJPBFRSK7CBFX655F2NGTBPICJSCYG2CSCQ5NRDHZG6QC
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