[lldb] Remove use of ConstString from Args::GetShellSafeArgument

[bulbazord]

Summary

Having the names of various shells in ConstString's StringPool is not
really necessary, especially if they are otherwise not going to be there
in the first place. For example, if the person debugging uses bash on
their system, the shell parameter will have its m_filename set to a
ConstString containing "bash". However, fish, tcsh, zsh, and sh will
probably never be used and are just taking up space in the StringPool.

lldb/source/Utility/Args.cpp

 //===-- Args.cpp ----------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "lldb/Utility/Args.h"
-#include "lldb/Utility/ConstString.h"
 #include "lldb/Utility/FileSpec.h"
 #include "lldb/Utility/Stream.h"
 #include "lldb/Utility/StringList.h"
 #include "llvm/ADT/StringSwitch.h"
 
 using namespace lldb;
 using namespace lldb_private;
 
void Args::Clear() {
   m_entries.clear();
   m_argv.clear();
   m_argv.push_back(nullptr);
 }
 
 std::string Args::GetShellSafeArgument(const FileSpec &shell,
                                        llvm::StringRef unsafe_arg) {
   struct ShellDescriptor {
-    ConstString m_basename;
+    llvm::StringRef m_basename;
     llvm::StringRef m_escapables;
   };
 
-  static ShellDescriptor g_Shells[] = {{ConstString("bash"), " '\"<>()&;"},
-                                       {ConstString("fish"), " '\"<>()&\\|;"},
-                                       {ConstString("tcsh"), " '\"<>()&;"},
-                                       {ConstString("zsh"), " '\"<>()&;\\|"},
-                                       {ConstString("sh"), " '\"<>()&;"}};
+  static ShellDescriptor g_Shells[] = {{"bash", " '\"<>()&;"},
+                                       {"fish", " '\"<>()&\\|;"},
+                                       {"tcsh", " '\"<>()&;"},
+                                       {"zsh", " '\"<>()&;\\|"},
+                                       {"sh", " '\"<>()&;"}};
 
   // safe minimal set
   llvm::StringRef escapables = " '\"";
 
-  if (auto basename = shell.GetFilename()) {
+  auto basename = shell.GetFilename().GetStringRef();
+  if (!basename.empty()) {
     for (const auto &Shell : g_Shells) {
       if (Shell.m_basename == basename) {
         escapables = Shell.m_escapables;
         break;
       }
     }
   }