* build-aux/hydra/gnu-system.scm (hydra-jobs): Pick all the `system' keys in ARGUMENTS. [cross-jobs]: Turn into a procedure, with a `system' parameter. Build packages for all of SYSTEMS and %CROSS-TARGETS.
* build-aux/hydra/gnu-system.scm (hydra-jobs): Pick all the `system' keys in ARGUMENTS. [cross-jobs]: Turn into a procedure, with a `system' parameter. Build packages for all of SYSTEMS and %CROSS-TARGETS.