bug#32161: seek out of range

[Ricardo Wurmus]

I’m getting this bug on berlin.guixsd.org.  The store is several hundred
GB in size.  I cannot reproduce this on a machine with a smaller store.

--8<---------------cut here---------------start------------->8---
In guix/store/deduplication.scm:
    62:18  1 (nar-sha256 _)
In unknown file:
           0 (seek #<output: string 11b20e0> 0 1)

ERROR: In procedure seek:
Value out of range -2147483648 to 2147483647: 4770726968
@ hook-failed 
/gnu/store/qjxwff3fajh350chpswbb6x9q2m4c3sd-texlive-texmf-2017.drv - 256 
builder for 
`/gnu/store/qjxwff3fajh350chpswbb6x9q2m4c3sd-texlive-texmf-2017.drv' failed 
with exit code 1
--8<---------------cut here---------------end--------------->8---

-- 
Ricardo