Implement new build rule: buildPackageLibrary.
Implement new build rule: buildPackageLibrary.

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