build-system/haskell: Generate Setup.hs if needed.

build-system/haskell: Generate Setup.hs if needed.

The default Setup.hs is boilerplate that is frequently left out of
source packages.  Several packages already add a phase to generate it,
so moving this phase to the build system is just factoring out an
existing pattern.

See <https://github.com/phadej/time-compat/issues/4>.

* guix/build/haskell-build-system.scm (generate-setuphs): New procedure.
(%standard-phases): Add it after 'unpack'.
* gnu/packages/haskell.scm (ghc-foundation, ghc-inline-c,
ghc-inline-c-cpp, ghc-rio): Remove 'arguments'.

Signed-off-by: Timothy Sample <samplet@ngyro.com>