bug#49418: Importing haskell packages from hackage doesn't apply metadata revisions

[Philip Munksgaard]

The hackage store of haskell packages allows maintainers to update package 
metadata directly on hackage without updating the associated archive of a 
package. For instance, the cabal file of the integer-logarithms package version 
1.0.3 [0] has been updated since 1.0.3 was published, relaxing the constraints 
on some dependencies[1]. This means that, if I try to build the attached 
integer-logarithms.scm (created from guix import hackage integer-logarithms and 
modified to use ghc-8.8) I get the following error:

```
Setup.hs: Encountered missing or private dependencies:
base >=4.3 && <4.13

command "runhaskell" "Setup.hs" "configure" 
"--prefix=/gnu/store/lssajarfg1vr6xbhi5dfvnn3xs01v3bz-ghc-integer-logarithms-bootstrap-1.0.3"
 
"--libdir=/gnu/store/lssajarfg1vr6xbhi5dfvnn3xs01v3bz-ghc-integer-logarithms-bootstrap-1.0.3/lib"
 
"--docdir=/gnu/store/lssajarfg1vr6xbhi5dfvnn3xs01v3bz-ghc-integer-logarithms-bootstrap-1.0.3/share/doc/ghc-integer-logarithms-bootstrap-1.0.3"
 "--libsubdir=$compiler/$pkg-$version" 
"--package-db=/tmp/guix-build-ghc-integer-logarithms-bootstrap-1.0.3.drv-0/package.conf.d"
 "--global" "--enable-shared" "--enable-executable-dynamic" 
"--ghc-option=-fPIC" 
"--ghc-option=-optl=-Wl,-rpath=/gnu/store/lssajarfg1vr6xbhi5dfvnn3xs01v3bz-ghc-integer-logarithms-bootstrap-1.0.3/lib/$compiler/$pkg-$version"
 failed with status 1
builder for 
`/gnu/store/pwdhhwp6d6b5g5pgik9y6ml5g1d8fxf5-ghc-integer-logarithms-bootstrap-1.0.3.drv'
 failed with exit code 1
build of 
/gnu/store/pwdhhwp6d6b5g5pgik9y6ml5g1d8fxf5-ghc-integer-logarithms-bootstrap-1.0.3.drv
 failed
```

In ghc 8.8 the base version is 4.13, and the updated cabal file for 
integer-logarithms amends the constrants to allow that version.

The solution might be to use `cabal get` to download the archive instead of 
downloading the .tar.gz directly, or manually amending the cabal file after 
downloading.

0: https://hackage.haskell.org/package/integer-logarithms-1.0.3
1: https://hackage.haskell.org/package/integer-logarithms-1.0.3/revisions/

integer-logarithms.scm
Description: Text Data