-cc_opt 'command_options'

   Specifies additional options to be passed to the C compiler. You
   can add options to the command line used to invoke the C compiler
   independent of the -cc_cmd argument.  The IDL compiler concatenates
   the -cc_cmd, -cc_opt, -I arguments and the source filename into a
   command that invokes the C compiler. This procedure is done for
   each generated stub or auxiliary file.  When used with the -lang
   cxx option, the -cc_opt option specifies the C++ compiler options.