Currently there are no tests that depend on the JDK. Since we don't
want a release with a broken JDK, make it an explicit dependency of
the "tested" jobs.
It now strictly evaluates all remaining attributes, preventing
unevaluated thunks that cannot be garbage-collected. It's also applied
to all jobs in Nixpkgs' release.nix.
This reduces hydra-eval-jobs' memory consumption on the 14.12
release-combined jobset from 5.1 GB to 2.0 GB.
This channel only builds a small subset of Nixpkgs, mostly suitable
for servers. Since the channel update doesn't require thousands of
packages to be built first, it should provide much faster turnaround
in case of security updates.
(cherry picked from commit 2c7acc6731)
