Remove dead code in driver parsing -gsimple-template-names= options

[probinson]

Summary

While -g[no-]simple-template-names is a driver option, the fancier
-gsimple-template-names={simple,mangled} option is cc1-only, so code
to handle it in the driver is dead.

[probinson]

Relevant quote from Options.td:

def gsimple_template_names : Flag<["-"], "gsimple-template-names">, Group<g_flags_Group>;
def gsimple_template_names_EQ
    : Joined<["-"], "gsimple-template-names=">,
      HelpText<"Use simple template names in DWARF, or include the full "
               "template name with a modified prefix for validation">,
      Values<"simple,mangled">, Flags<[CC1Option, NoDriverOption]>;
def gno_simple_template_names : Flag<["-"], "gno-simple-template-names">,
                                Group<g_flags_Group>;

[dblaikie]

oh, fair - yeah, if the tests pass, sounds good to me.

[probinson]

+cfe-commits; that should have happened automatically?

clang/lib/Driver/ToolChains/Clang.cpp

if (DwarfFission != DwarfFissionKind::None ||
     if (!PubnamesArg ||
         (!PubnamesArg->getOption().matches(options::OPT_gno_gnu_pubnames) &&
          !PubnamesArg->getOption().matches(options::OPT_gno_pubnames)))
       CmdArgs.push_back(PubnamesArg && PubnamesArg->getOption().matches(
                                            options::OPT_gpubnames)
                             ? "-gpubnames"
                             : "-ggnu-pubnames");
   const auto *SimpleTemplateNamesArg =
-      Args.getLastArg(options::OPT_gsimple_template_names, options::OPT_gno_simple_template_names,
-                      options::OPT_gsimple_template_names_EQ);
+      Args.getLastArg(options::OPT_gsimple_template_names,
+                      options::OPT_gno_simple_template_names);
   bool ForwardTemplateParams = DebuggerTuning == llvm::DebuggerKind::SCE;
   if (SimpleTemplateNamesArg &&
       checkDebugInfoOption(SimpleTemplateNamesArg, Args, D, TC)) {
     const auto &Opt = SimpleTemplateNamesArg->getOption();
     if (Opt.matches(options::OPT_gsimple_template_names)) {
       ForwardTemplateParams = true;
       CmdArgs.push_back("-gsimple-template-names=simple");
-    } else if (Opt.matches(options::OPT_gsimple_template_names_EQ)) {
-      ForwardTemplateParams = true;
-      StringRef Value = SimpleTemplateNamesArg->getValue();
-      if (Value == "simple") {
-        CmdArgs.push_back("-gsimple-template-names=simple");
-      } else if (Value == "mangled") {
-        CmdArgs.push_back("-gsimple-template-names=mangled");
-      } else {
-        D.Diag(diag::err_drv_unsupported_option_argument)
-            << Opt.getName() << SimpleTemplateNamesArg->getValue();
-      }
     }
   }
 
   if (Args.hasFlag(options::OPT_fdebug_ranges_base_address,
                    options::OPT_fno_debug_ranges_base_address, false)) {
     CmdArgs.push_back("-fdebug-ranges-base-address");
   }