Handling of command line invalid options

[bright-tools]

The LLVM commandline parser deals with arguments which are syntactically incorrect, but doesn't deal with options which are invalid. An example of this is specifying an output file which cannot be opened (invalid file name, file permissions, etc).

The approach in LLVM to dealing with this is to simply exit during the parsing process rather than to pass the information back to the caller. It would make sense to adopt the same approach in CCSM.