bug#53696: Integer overflow on Guix GC size calculation

[Ekaitz Zarraga]

Hi,

I noticed there's some kind of a wierd integer overflow on the size calculation 
on `guix gc`:

[17592186042896 MiB] deleting 
'/gnu/store/j2s6kva8l20m6rjj10bnknq99jc9rg6w-ghc-random-1.2.0-builder'
[17592186042896 MiB] deleting 
'/gnu/store/8nx7zzj629qvv1533c48bl19wrkwcjh2-curl-7.79.1-doc'
[17592186042897 MiB] deleting 
'/gnu/store/dcsi13588yyjws76s1wjc7h5spnjd2vn-ghc-kan-extensions-5.2.3-builder'
[17592186042897 MiB] deleting 
'/gnu/store/5zrhw6kvb8wd3n6lazpblqzsg92y320b-ghc-sop-core-0.5.0.1-builder'
[17592186042897 MiB] deleting 
'/gnu/store/l2ya1z3la9qfdj9139f09q3djs36lw3l-ghc-aeson-pretty-0.8.9-builder'
[17592186042897 MiB] deleting 
'/gnu/store/8a8nbfxq508r7qywkhaw8jj8hicpfjh8-ghc-prelude-extras-0.4.0.3-builder'
[17592186042897 MiB] deleting 
'/gnu/store/wbz6vkiz7cq8c531xvb31lxm28nz332i-ghc-8.10.7'
[19 MiB] deleting '/gnu/store/i5np7ifiabg333g2l8ycmvbhimnrrx8k-ghc-8.10.7-doc'
[170 MiB] deleting 
'/gnu/store/yx9zjw9118gzfcx33adfwy6kghrzxkys-ghc-pem-0.2.4-builder'
[170 MiB] deleting 
'/gnu/store/pinvkg1x5rpsgm95zhn50l6xq7rly43f-perl-test-output-1.033.drv'
[170 MiB] deleting 
'/gnu/store/k1bdc950d62g1pw4yw1khgmfr32m3rpm-perl-sub-exporter-0.988.drv'