Distribution/Gentoo/GHC.hs: port to Cabal-1.18

rawSystemStdInOut got two more arguments in cabal-1.18+

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
haskell-updater.cabal: release 1.2.0.11

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>