[Nix-dev] Force Hydra to use localhost for building

[Peter Simons]

Hi Nikolay,,

 > Unfortunately, with distributed build enabled Hydra doesn't use its
 > own server for building at all.

it does, but only if all remote machines are busy. If you have build
slaves with a configured maximum capacity of n jobs, then the n+1-th
parallel build job (and all beyond that) will run on localhost.

It's an imperfect situation.

Best regards,
Peter