[arch-haskell] [PATCH] Adapt to recent style changes for PKGBUILDs

This patch modifies cabal2arch to adapt to recent changes in makepkg : * the "|| return 1" are not needed, the build function exits automatically when encountering errors * the build() function is now split into the build() function and the package() function, such that build() never touches $pkgdir. -- Rémy.