convert all readFile, writeFile, and appendFile to close-on-exec safe versions

Even in the Build system. This allows grepping to make sure that there
are none left un-converted:

git grep "writeFile" |grep -v F\\.| grep -v doc/|grep -v writeFileString | grep -v writeFileProtected |grep -v Utility/FileIO
git grep "readFile" |grep -v F\\.| grep -v doc/|grep -v readFileString |grep -v Utility/FileIO
git grep "appendFile" |grep -v F\\.| grep -v doc/|grep -v appendFileString |grep -v Utility/FileIO

Might be nice to automate that to prevent future mistakes...

Sponsored-by: the NIH-funded NICEMAN (ReproNim TR&D3) project

Command/FuzzTest.hs

@@ -178,7 +178,7 @@ runFuzzAction :: FuzzAction -> Annex ()
 runFuzzAction (FuzzAdd (FuzzFile f)) = do
 	createWorkTreeDirectory (parentDir (toOsPath f))
 	n <- liftIO (getStdRandom random :: IO Int)
-	liftIO $ writeFile f $ show n ++ "\n"
+	liftIO $ writeFileString (toOsPath f) $ show n ++ "\n"
 runFuzzAction (FuzzDelete (FuzzFile f)) = liftIO $
 	removeWhenExistsWith removeFile (toOsPath f)
 runFuzzAction (FuzzMove (FuzzFile src) (FuzzFile dest)) = liftIO $