bug#47908: Cross building disk image for ARM Asus C201 fails

[Martin via Bug reports for GNU Guix <bug-guix@gnu.org>]

Hello,
I'm trying to create a disk image for an Asus C201 chromebook using the 
command 'guix system image test.scm' where test.scm based on 
https://github.com/guix-mirror/guix/blob/master/gnu/system/examples/asus-c201.tmpl 
but unfortunately this operation fails on my x86 dev machine (guix 53ed3e4):

---
  yaml-0.2.5.tar.gz  595KiB                                  4.0MiB/s 
00:00 [##################] 100.0%
  zstd-1.4.4.tar.xz  1.3MiB                                  2.9MiB/s 
00:00 [##################] 100.0%
building /gnu/store/ifnczywhsw1x5wijrv60myv309g7vqg0-libyaml-0.2.5.drv...
building 
/gnu/store/fi24bh8iqrwqby2224n602vd0x2gvz81-python-minimal-3.8.2.drv...
building 
/gnu/store/z2diqxmpr8zkiyk2d5vma4flwvd3bzk6-vboot-utils-R63-10032.B.drv...
- 'patch-hard-coded-paths' phasebuilder for 
`/gnu/store/z2diqxmpr8zkiyk2d5vma4flwvd3bzk6-vboot-utils-R63-10032.B.drv' 
failed with exit code 1
build of 
/gnu/store/z2diqxmpr8zkiyk2d5vma4flwvd3bzk6-vboot-utils-R63-10032.B.drv 
failed
View build log at 
'/var/log/guix/drvs/z2/diqxmpr8zkiyk2d5vma4flwvd3bzk6-vboot-utils-R63-10032.B.drv.bz2'.
guix system: error: build of 
`/gnu/store/z2diqxmpr8zkiyk2d5vma4flwvd3bzk6-vboot-utils-R63-10032.B.drv' 
failed
---

the logs:
---
vboot-utils-R63-10032.B-checkout/vboot_host.pc.in
phase `unpack' succeeded after 1.1 seconds
starting phase `patch-hard-coded-paths'
Backtrace:
           16 (primitive-load "/gnu/store/3px9vwr51v82zhh7bzi8wcmiaw3…")
In ice-9/eval.scm:
    191:35 15 (_ #f)
In guix/build/gnu-build-system.scm:
     838:2 14 (gnu-build #:source _ #:outputs _ #:inputs _ #:phases . #)
In ice-9/boot-9.scm:
   1736:10 13 (with-exception-handler _ _ #:unwind? _ # _)
In srfi/srfi-1.scm:
    857:16 12 (every1 #<procedure 7ffff5f6d120 at guix/build/gnu-bui…> …)
In guix/build/gnu-build-system.scm:
    847:30 11 (_ _)
In ice-9/eval.scm:
     619:8 10 (_ #(#(#(#<directory (guile-user) 7ffff6bb9f00>) # #) …))
In ice-9/boot-9.scm:
   1736:10  9 (with-exception-handler _ _ #:unwind? _ # _)
In ice-9/ports.scm:
    445:17  8 (call-with-input-file _ _ #:binary _ #:encoding _ # _)
In guix/build/utils.scm:
    741:26  7 (_ _)
    767:26  6 (_ #<input: tests/bitmaps/TestBmpBlock.py 15> #<input-o…>)
In srfi/srfi-1.scm:
    460:18  5 (fold #<procedure 7ffff6a7c040 at guix/build/utils.scm…> …)
In ice-9/eval.scm:
    202:51  4 (_ #(#(#(#(#(#(#<directory (guile-user)…> …)) …) …) …) …))
     163:9  3 (_ #(#(#(#(#(#(#<directory (guile-user)…> …)) …) …) …) …))
In unknown file:
            2 (string-append #f "/bin/cmp")
In ice-9/boot-9.scm:
   1669:16  1 (raise-exception _ #:continuable? _)
   1669:16  0 (raise-exception _ #:continuable? _)

ice-9/boot-9.scm:1669:16: In procedure raise-exception:
In procedure string-append: Wrong type (expecting string): #f
---

Any ideas how to fix it or do you know some alternative approaches how 
to install GuixSD on Asus C201?

Thanks,
Martin