Refactor mkFlag out of old packages

pkgs/tools/filesystems/ceph/generic.nix

@@ -28,13 +28,6 @@ assert cryptopp != null || (nss != null && nspr != null);
 
 with stdenv.lib;
 let
-  mkFlag = trueStr: falseStr: cond: name: val:
-    if cond == null then null else
-      "--${if cond != false then trueStr else falseStr}${name}${if val != null && cond != false then "=${val}" else ""}";
-  mkEnable = mkFlag "enable-" "disable-";
-  mkWith = mkFlag "with-" "without-";
-  mkOther = mkFlag "" "" true;
-
   hasServer = snappy != null && leveldb != null;
   hasMon = hasServer;
   hasMds = hasServer;