Support --debug, it's just an alias of -d

* Already handled as a nomal option, no need for special parsing.

Author: eregon

src/launcher/java/org/truffleruby/launcher/CommandLineParser.java

@@ -416,8 +416,6 @@ private void processArgument() throws CommandLineException {
                         final String encodingName = argument.substring(argument.indexOf('=') + 1);
                         config.setOption(OptionsCatalog.INTERNAL_ENCODING, encodingName);
                         break FOR;
-                    } else if (argument.equals("--debug")) {
-                        throw notImplemented("--debug");
                     } else if (argument.equals("--yydebug")) {
                         disallowedInRubyOpts(argument);
                         warnInternalDebugTool(argument);