Slightly sped up the linux standalone bundle

Reduce the number of directories listed in libdirs, which makes the linker
check a lot less dead ends looking for directories.

Eliminated some directories that didn't really contain shared libraries,
or only contained the linker.

That left only 2, one in lib and one in usr/lib, so consolidate those two.

Doing it this way, rather than just consolidating all libs that might exist
into a single directory means that, if there are optimised versions of some
libs, eg in lib/subarch/foo.so, and lib/subarch2/foo.so, they don't get
moved around in a way that would make the linker pick the wrong one.

Build/LinuxMkLibs.hs

@@ -36,18 +36,51 @@ mklibs top = do
 	fs <- dirContentsRecursive top
 	exes <- filterM checkExe fs
 	libs <- parseLdd <$> readProcess "ldd" exes
+	
 	glibclibs <- glibcLibs
 	let libs' = nub $ libs ++ glibclibs
-	libdirs <- nub . catMaybes <$> mapM (installLib installFile top) libs'
+	let (linkers, otherlibs) = partition ("ld-linux" `isInfixOf`) libs'
+	libdirs <- nub . catMaybes <$> mapM (installLib installFile top) otherlibs
+	libdirs' <- consolidateUsrLib top libdirs
+
+	gconvlibs <- gconvLibs
+	mapM_ (installLib installFile top) gconvlibs
 
 	-- Various files used by runshell to set up env vars used by the
 	-- linker shims.
-	writeFile (top </> "libdirs") (unlines libdirs)
-	writeFile (top </> "gconvdir")
-		(parentDir $ Prelude.head $ filter ("/gconv/" `isInfixOf`) glibclibs)
+	writeFile (top </> "libdirs") (unlines libdirs')
+	writeFile (top </> "gconvdir") (parentDir $ Prelude.head gconvlibs)
 	
-	let linker = Prelude.head $ filter ("ld-linux" `isInfixOf`) libs'
+	mapM_ (installLib installFile top) linkers
+	let linker = Prelude.head linkers
 	mapM_ (installLinkerShim top linker) exes
+	
+{- If there are two libdirs that are the same except one is in
+ - usr/lib and the other is in lib/, move the contents of the usr/lib one
+ - into the lib/ one. This reduces the number of directories the linker
+ - needs to look in, and so reduces the number of failed stats
+ - and improves startup time.
+ -}
+consolidateUsrLib :: FilePath -> [FilePath] -> IO [FilePath]
+consolidateUsrLib top libdirs = map reverse <$> go [] (map reverse libdirs)
+  where
+	go c [] = return c
+	go c (x:[]) = return (x:c)
+	go c (x:y:rest)
+		| x == y ++ reverse ("/usr") = do
+			let x' = reverse x
+			let y' = reverse y
+			fs <- getDirectoryContents (inTop top x')
+			forM_ fs $ \f -> do
+				print f
+				unless (dirCruft f) $
+					renameFile 
+						(inTop top (x' </> f))
+						(inTop top (y' </> f))
+			go (y:c) rest
+		| otherwise = do
+			print (x,y)
+			go (x:c) (y:rest)
 
 {- Installs a linker shim script around a binary.
  -