[bug#49199] [PATCH core-updates] add package-db to runhaskell (haskell-build-system)

[John Kehayias]

Hello,

This is a patch to fix issue #48944 as well as more broadly an issue of Haskell 
packages that need modules at the configure step. Currently the package 
database is not passed to runhaskell directly, which means runhaskell Setup.hs 
configure does not have outside modules available. This blocks packages that 
need things like cabal-doctest or gtk2hs-buildtools like ghc-cairo (which has a 
custom build process in the package currently, for this reason). Comments in 
ghc-cairo and for other packages with this need, suggest the change made in 
this patch.

The simplest change I saw was to make the package database passed to runhaskell 
on any command; not sure if this would be better for just configure. It may be 
possible to do this just passing the actual needed packages with -package-id, 
as suggested in https://github.com/tweag/rules_haskell/issues/1314 However, I 
have not tried that and seemed more complicated than needed. Also, I did not 
modify the message printed as it already has the package-db in params, but 
perhaps better to be clear the exact command being run?

I have built many Haskell packages with this change and it works well for me, 
fixing the reported issue and packages I'm building not yet in guix. Given this 
changes the build command for all Haskell packages, would be happy for other 
tests to be run.

John

runhaskell-add-pkgdb.patch
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