Refactor package-data generation for custom packages
Refactor package-data generation for custom packages

sdiehl/ghc,sdiehl/ghc,bgamari/shaking-up-ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,izgzhen/hadrian,snowleopard/shaking-up-ghc,sdiehl/ghc,sdiehl/ghc,snowleopard/hadrian