[Driver][NFC] Initialize an uninitialized variable (#10126)

Clean up some logically dead code.

Author: hchilama

clang/lib/Driver/Driver.cpp

@@ -203,7 +203,7 @@ Driver::Driver(StringRef ClangExecutable, StringRef TargetTriple,
     : Diags(Diags), VFS(std::move(VFS)), Mode(GCCMode),
       SaveTemps(SaveTempsNone), BitcodeEmbed(EmbedNone),
       Offload(OffloadHostDevice), CXX20HeaderType(HeaderMode_None),
-      ModulesModeCXX20(false), LTOMode(LTOK_None),
+      ModulesModeCXX20(false), LTOMode(LTOK_None), OffloadLTOMode(LTOK_None),
       ClangExecutable(ClangExecutable), SysRoot(DEFAULT_SYSROOT),
       DriverTitle(Title), CCCPrintBindings(false), CCPrintOptions(false),
       CCLogDiagnostics(false), CCGenDiagnostics(false),

clang/lib/Driver/ToolChains/CommonArgs.cpp

@@ -908,8 +908,6 @@ bool tools::addOpenMPRuntime(ArgStringList &CmdArgs, const ToolChain &TC,
   case Driver::OMPRT_IOMP5:
     CmdArgs.push_back("-liomp5");
     break;
-  case Driver::OMPRT_Unknown:
-    break;
   }
 
   if (ForceStaticHostRuntime)
@@ -1815,8 +1813,6 @@ static void AddUnwindLibrary(const ToolChain &TC, const Driver &D,
     CmdArgs.push_back(getAsNeededOption(TC, true));
 
   switch (UNW) {
-  case ToolChain::UNW_None:
-    return;
   case ToolChain::UNW_Libgcc: {
     if (LGT == LibGccType::StaticLibGcc)
       CmdArgs.push_back("-lgcc_eh");