Mark pre-merge pipeline as failed if any target fails

[joinemm]

Reusing the error handling logic from utils.groovy. The reason we can't just use the nix_build from utils is that it's not equipped to deal with raw derivation paths, and expects a flake reference. There is also lot of unnecessary steps not suitable for parallel building, such as signing and artifact archiving.

[henrirosten]

> The reason we can't just use the nix_build from utils is that it's not equipped to deal with raw derivation paths, and expects a flake reference. There is also lot of unnecessary steps not suitable for parallel building, such as signing and artifact archiving.

Not necessary a topic of this PR, but:
I assume we are going to soon make the other pipelines (main, nightly, release) build parallel too, so we probably should modify the relevant functions in utils.groovy in such a way that they could be called from such parallel build pipelines too.

[joinemm]

yes, but for now this is the easier way to not break every other pipeline in the process