Compute package dependencies only for packages we build

See #265

src/Rules/Cabal.hs

@@ -16,7 +16,7 @@ cabalRules :: Rules ()
 cabalRules = do
     -- Cache boot package constraints (to be used in 'cabalArgs').
     bootPackageConstraints %> \out -> do
-        bootPkgs <- interpretInContext (stageContext Stage0) getPackages
+        bootPkgs <- stagePackages Stage0
         let pkgs = filter (\p -> p /= compiler && isLibrary p) bootPkgs
         constraints <- forM (sort pkgs) $ \pkg -> do
             need [pkgCabalFile pkg]
@@ -28,7 +28,8 @@ cabalRules = do
 
     -- Cache package dependencies.
     packageDependencies %> \out -> do
-        pkgDeps <- forM (sort knownPackages) $ \pkg ->
+        pkgs <- concatMapM stagePackages [Stage0 .. Stage2]
+        pkgDeps <- forM (sort pkgs) $ \pkg ->
             if pkg `elem` [hp2ps, libffi, rts, touchy, unlit]
             then return $ pkgNameString pkg
             else do

src/Rules/Test.hs

@@ -23,7 +23,7 @@ testRules = do
 
     "test" ~> do
         let yesNo x = show $ if x then "YES" else "NO"
-        pkgs     <- interpretInContext (stageContext Stage1) getPackages
+        pkgs     <- stagePackages Stage1
         tests    <- filterM doesDirectoryExist $ concat
                     [ [ pkgPath pkg -/- "tests", pkgPath pkg -/- "tests-ghc" ]
                     | pkg <- pkgs, isLibrary pkg, pkg /= rts, pkg /= libffi ]

src/Settings.hs

 module Settings (
     getArgs, getPackages, getLibraryWays, getRtsWays, flavour, knownPackages,
     findKnownPackage, getPkgData, getPkgDataList, isLibrary, getPackagePath,
-    getContextDirectory, getBuildPath
+    getContextDirectory, getBuildPath, stagePackages
     ) where
 
 import Base
@@ -28,6 +28,9 @@ getRtsWays = fromDiffExpr $ rtsWays flavour
 getPackages :: Expr [Package]
 getPackages = fromDiffExpr $ packages flavour
 
+stagePackages :: Stage -> Action [Package]
+stagePackages stage = interpretInContext (stageContext stage) getPackages
+
 getPackagePath :: Expr FilePath
 getPackagePath = pkgPath <$> getPackage
 

src/Settings/Default.hs

@@ -65,7 +65,6 @@ defaultBuilderArgs = mconcat
     , makeBuilderArgs
     , tarBuilderArgs ]
 
-
 -- | All 'Package'-dependent command line arguments.
 defaultPackageArgs :: Args
 defaultPackageArgs = mconcat