It's hard/impossible to use builds from another jobset as a dependency with the new package convention

In the new packaging convention, every build job is bound to a system architecture. For example, build.x86_64-linux, builds a particular package for x86-64-linux.

However, using this new convention makes it difficult (or I would say: almost impossible) for a jobset to refer to an existing build result for the same architecture belonging to a different jobset.

In the old convention, I could directly address an existing build result through. project:jobset:job and pick the 'Build result (same system)' to use a build result from another jobset.

Although Hydra still supports this old feature, it can no longer be used with a release expression following the new convention.

I know two possible solutions. One solution is to allow a release expression to refer to a jobset result, e.g. through an attribute set referring to builtins.storePath invocations.

Another solutions is to adapt the 'Build result (same system)' option to use the new convention (e.g. by automatically referring to the desired system architecture sub attribute).

No files or tests are named. Start by examining release-expression handling and the “Build result (same system)” option, then compare the two proposed approaches. Done should allow a release expression using the new package convention to reuse a build result for the same architecture from another jobset.