'./pre-inst-env guix build xxx' can not find packages in other channels.

[Feng Shu]

Hello, 

I use the below channel setting:

  (service
       home-channels-service-type
       (cons* (channel
               (name 'nonguix)
               (url "https://gitlab.com/nonguix/nonguix";)
               ;; Enable signature verification:
               (introduction
                (make-channel-introduction
                 "897c1a470da759236cc11798f4e0a5f7d4d59fbc"
                 (openpgp-fingerprint
                  "2A39 3FFF 68F4 EF7A 3D29  12AF 6F51 20A0 22FB B2D5"))))
              %default-channels))


but when I run 

  ./pre-inst-env guix build unrar


it can not find unrar, for unrar is a package in nonguix channel. use -L
seem to work:

  ./pre-inst-env guix build unrar -L /path/to/nonguix.git

my question is: how to let pre-inst-env work well with my channel
setting, and no need to use -L in every command.


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