bug#70877: guix-daemon fails to copy 4+GB file to store

[Ludovic Courtès]

BTW, the newly updated ‘guix’ package is 8% smaller, as a result of
<https://issues.guix.gnu.org/70398>:

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$ guix describe 
Generation 302  May 12 2024 23:29:11    (current)
  guix 89cd778
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: 89cd778f6a45cd9b43a4dc1f236dcd0a87af955c
$ guix size guix |head -2
store item                                                       total    self
/gnu/store/r96xq0064nqf43ygcr7z9lgb18vrd1wa-guix-1.4.0-18.4c94b9e   705.8   
400.6  56.8%
$ ./pre-inst-env guix size guix |head -2
store item                                                       total    self
/gnu/store/mcw1d2zy96is5ymjj903i3bi5a0qdwr5-guix-1.4.0-19.7ca9809   673.8   
368.7  54.7%
$ git log |head -1
commit 58be9a79e2862d5fa9842d73f498ce2e5442b9ce
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Ludo’.