Makefile now builds using cabal, taking advantage of cabal's automatic detection of appropriate build flags.

The only thing lost is ./ghci

Speed: make fast used to take 20 seconds here, when rebuilding from
touching Command/Unused.hs. With cabal, it's 29 seconds.

Annex/Branch.hs

@@ -287,7 +287,7 @@ withIndex' :: Bool -> Annex a -> Annex a
 withIndex' bootstrapping a = do
 	f <- fromRepo gitAnnexIndex
 	g <- gitRepo
-#ifdef WITH_ANDROID
+#ifdef __ANDROID__
 	{- Work around for weird getEnvironment breakage on Android. See
 	 - https://github.com/neurocyte/ghc-android/issues/7
 	 - Instead, use getEnv to get some key environment variables that