Use override syntax that rebar3 accepts

plugins/override_opts.erl

@@ -2,11 +2,11 @@
 -export([preprocess/2]).
 
 override_opts(override, Config, Opts) ->
-    lists:foldl(fun({Opt, Value}, Conf) ->
+    lists:foldl(fun({Opt, [Value]}, Conf) ->
 			rebar_config:set(Conf, Opt, Value)
 		end, Config, Opts);
 override_opts(add, Config, Opts) ->
-    lists:foldl(fun({Opt, Value}, Conf) ->
+    lists:foldl(fun({Opt, [Value]}, Conf) ->
 			V = rebar_config:get_local(Conf, Opt, []),
 			rebar_config:set(Conf, Opt, [Value | V])
 		end, Config, Opts).

rebar.config.script

@@ -298,8 +298,8 @@ GenDepsConfigure =
 fun(Hooks) ->
 	lists:map(fun({Pkg, Flags}) ->
 			  DepPath = ResolveDepPath("deps/" ++ Pkg ++ "/"),
-			  {add, list_to_atom(Pkg), [{pre_hooks, {'compile',
-			   lists:flatten(GenDepConfigureLine(DepPath, Flags))}}]}
+			  {add, list_to_atom(Pkg), [{pre_hooks, [{'compile',
+			   lists:flatten(GenDepConfigureLine(DepPath, Flags))}]}]}
 		  end, Hooks)
 end,