[Driver] print-multi-os-directory is unsupported

[davide]

Summary

Until somebody writes the code for it, be loud about the fact that it's not implemented yet.

[jroelofs]

LGTM

include/clang/Driver/Options.td

 def print_file_name_EQ : Joined<["-", "--"], "print-file-name=">,
   HelpText<"Print the full library path of <file>">, MetaVarName<"<file>">;
 def print_ivar_layout : Flag<["-"], "print-ivar-layout">, Flags<[CC1Option]>,
   HelpText<"Enable Objective-C Ivar layout bitmap print trace">;
 def print_libgcc_file_name : Flag<["-", "--"], "print-libgcc-file-name">,
   HelpText<"Print the library path for \"libgcc.a\"">;
 def print_multi_directory : Flag<["-", "--"], "print-multi-directory">;
 def print_multi_lib : Flag<["-", "--"], "print-multi-lib">;
-def print_multi_os_directory : Flag<["-", "--"], "print-multi-os-directory">;
+def print_multi_os_directory : Flag<["-", "--"], "print-multi-os-directory">,
+  Flags<[Unsupported]>;
 def print_prog_name_EQ : Joined<["-", "--"], "print-prog-name=">,
   HelpText<"Print the full program path of <name>">, MetaVarName<"<name>">;
 def print_search_dirs : Flag<["-", "--"], "print-search-dirs">,
   HelpText<"Print the paths used for finding libraries and programs">;
 def private__bundle : Flag<["-"], "private_bundle">;
 def pthreads : Flag<["-"], "pthreads">;
 def pthread : Flag<["-"], "pthread">, Flags<[CC1Option]>,
   HelpText<"Support POSIX threads in generated code">;

lib/Driver/Driver.cpp

       else {
         StringRef Suffix(Multilib.gccSuffix());
         assert(Suffix.front() == '/');
         llvm::outs() << Suffix.substr(1) << "\n";
       }
     }
     return false;
   }
-
-  if (C.getArgs().hasArg(options::OPT_print_multi_os_directory)) {
-    // FIXME: This should print out "lib/../lib", "lib/../lib64", or
-    // "lib/../lib32" as appropriate for the toolchain. For now, print
-    // nothing because it's not supported yet.
-    return false;
-  }
-
   return true;
 }
 
 // Display an action graph human-readably.  Action A is the "sink" node
 // and latest-occuring action. Traversal is in pre-order, visiting the
 // inputs to each action before printing the action itself.
 static unsigned PrintActions1(const Compilation &C, Action *A,
                               std::map<Action *, unsigned> &Ids) {