-C flag does not actually chdir before run

[headius]

From http://jira.codehaus.org/browse/JRUBY-7090

When passing -C at the command line, we first boot the JVM and then process the chdir as a "virtual" chdir just for the JRuby instance. JRuby code will then see the virtual cwd, but other code within the JVM will only see the real cwd.

We could fix this by doing a real chdir before running the JVM, or by forcibly chdir'ing the JVM (probably only when we know -C was passed as a command-line arg.