`guix pack --target=arm-linux-gnueabihf guile` fails at phase unpack

[Louis Pearson]

I am experimenting with different methods of building applications and
deploying them to embedded devices. I am currently experimenting with
`guix` and the `guix pack` command. When running `guix pack
--target=arm-linux-gnueabihf guile` with guile however, I encounter
this error:

```
starting phase `set-SOURCE-DATE-EPOCH'
phase `set-SOURCE-DATE-EPOCH' succeeded after 0.0 seconds
starting phase `set-paths'
environment variable `PATH' set to
`/gnu/store/4jqlvfhg05jmamjf54qshgwadkrmv8mx-gcc-cross-x86_64-linux-5.4.0/bin:/gnu/store/yvkc7dchld236jkyplsdmzyf01armvap-binutils-cross-x86_64-linux-2.27/bin'
environment variable `CROSS_LIBRARY_PATH' set to
`/gnu/store/3i1rnjjq8sjfwc6312ri3wvl225yjy08-glibc-bootstrap-0/lib:/gnu/store/vi8s8ycw11ai753rp5yb4ss76xwl5y72-gcc-bootstrap-0/lib:/gnu/store/c2yma1ycj8gfzbvd7p44r08s8lk5ss3w-glibc-cross-x86_64-linux-2.25/lib'
environment variable `CROSS_C_INCLUDE_PATH' set to
`/gnu/store/3i1rnjjq8sjfwc6312ri3wvl225yjy08-glibc-bootstrap-0/include:/gnu/store/vi8s8ycw11ai753rp5yb4ss76xwl5y72-gcc-bootstrap-0/include:/gnu/store/c2yma1ycj8gfzbvd7p44r08s8lk5ss3w-glibc-cross-x86_64-linux-2.25/include:/gnu/store/kbjhc370r0b2vbwxr5383jncsw633gj9-linux-libre-headers-cross-x86_64-linux-4.4.47/include'
environment variable `CROSS_CPLUS_INCLUDE_PATH' set to
`/gnu/store/3i1rnjjq8sjfwc6312ri3wvl225yjy08-glibc-bootstrap-0/include:/gnu/store/vi8s8ycw11ai753rp5yb4ss76xwl5y72-gcc-bootstrap-0/include:/gnu/store/c2yma1ycj8gfzbvd7p44r08s8lk5ss3w-glibc-cross-x86_64-linux-2.25/include:/gnu/store/kbjhc370r0b2vbwxr5383jncsw633gj9-linux-libre-headers-cross-x86_64-linux-4.4.47/include'
environment variable `CROSS_OBJC_INCLUDE_PATH' set to
`/gnu/store/3i1rnjjq8sjfwc6312ri3wvl225yjy08-glibc-bootstrap-0/include:/gnu/store/vi8s8ycw11ai753rp5yb4ss76xwl5y72-gcc-bootstrap-0/include:/gnu/store/c2yma1ycj8gfzbvd7p44r08s8lk5ss3w-glibc-cross-x86_64-linux-2.25/include:/gnu/store/kbjhc370r0b2vbwxr5383jncsw633gj9-linux-libre-headers-cross-x86_64-linux-4.4.47/include'
environment variable `CROSS_OBJCPLUS_INCLUDE_PATH' set to
`/gnu/store/3i1rnjjq8sjfwc6312ri3wvl225yjy08-glibc-bootstrap-0/include:/gnu/store/vi8s8ycw11ai753rp5yb4ss76xwl5y72-gcc-bootstrap-0/include:/gnu/store/c2yma1ycj8gfzbvd7p44r08s8lk5ss3w-glibc-cross-x86_64-linux-2.25/include:/gnu/store/kbjhc370r0b2vbwxr5383jncsw633gj9-linux-libre-headers-cross-x86_64-linux-4.4.47/include'
environment variable `GUIX_LOCPATH' unset
environment variable `CPATH' set to
`/gnu/store/4jqlvfhg05jmamjf54qshgwadkrmv8mx-gcc-cross-x86_64-linux-5.4.0/include'
environment variable `LIBRARY_PATH' set to
`/gnu/store/4jqlvfhg05jmamjf54qshgwadkrmv8mx-gcc-cross-x86_64-linux-5.4.0/lib'
phase `set-paths' succeeded after 0.0 seconds
starting phase `install-locale'
warning: failed to install 'en_US.utf8' locale: Invalid argument
phase `install-locale' succeeded after 0.0 seconds
starting phase `unpack'
In execvp of tar: No such file or directory
phase `unpack' failed after 0.0 seconds
builder for `/gnu/store/2igq71k5767mh00wwii6lw7b04yq753s-make-boot0-4.2.1.drv'
failed with exit code 1
cannot build derivation
`/gnu/store/xbwfrk8q029di2y7wbkb70x5j67b5zka-gcc-cross-boot0-5.4.0.drv':
1 dependencies couldn't be built
guix pack: error: build failed: build of
`/gnu/store/xbwfrk8q029di2y7wbkb70x5j67b5zka-gcc-cross-boot0-5.4.0.drv'
failed

```

What is going on? The important part appears to be `In execvp of tar:
No such file or directory`, but I'm not sure why tar is unable to find
the file/directory.