bug#60786: cross-kernel-headers can produce broken packages

[Maxim Cournoyer]

Hello,

This issue was triggered by having make-uboot-package uses #:target [0],
but it already exists on current master.  I've spent some time narrowing
down the issue, and it is caused by the package returned by
cross-kernel-headers in (gnu packages cross-base) being produced with a
bogus arguments field, or at least one that can't be access via the
package-arguments accessor:

--8<---------------cut here---------------start------------->8---
(use-modules (guix packages)
             (gnu packages cross-base))

(define linux-libre-headers-cross-mips64el-linux-gnuabi64
  (cross-kernel-headers "mips64el-linux-gnuabi64"))

(package-arguments linux-libre-headers-cross-mips64el-linux-gnuabi64)

ice-9/boot-9.scm:1685:16: In procedure raise-exception:
In procedure struct-vtable: Wrong type argument in position 1 (expecting 
struct): #f

Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
scheme@(guix-user) [1]> ,bt
In gnu/packages/cross-base.scm:
   388:33  1 (loop (#:phases (modify-phases %standard-phases (delete (quote 
configure)) (# (…) …) …) …) …)
In ice-9/boot-9.scm:
  1685:16  0 (raise-exception _ #:continuable? _)
--8<---------------cut here---------------end--------------->8---

[0]  https://issues.guix.gnu.org/60224#30

-- 
Thanks,
Maxim