Add pkgs.lib.renderOptions

This adds a new utility to intelligently convert Nix records to
command line options to reduce boilerplate for simple use cases and to
also reduce the likelihood of malformed command lines

lib/default.nix

@@ -39,6 +39,7 @@ let
 
     # misc
     asserts = callLibs ./asserts.nix;
+    cli = callLibs ./cli.nix;
     debug = callLibs ./debug.nix;
     generators = callLibs ./generators.nix;
     misc = callLibs ./deprecated.nix;
@@ -120,6 +121,7 @@ let
       isOptionType mkOptionType;
     inherit (asserts)
       assertMsg assertOneOf;
+    inherit (cli) renderOptions;
     inherit (debug) addErrorContextToAttrs traceIf traceVal traceValFn
       traceXMLVal traceXMLValMarked traceSeq traceSeqN traceValSeq
       traceValSeqFn traceValSeqN traceValSeqNFn traceShowVal