[lldb] Add missing mutex guards to TargetList::CreateTarget

[teemperor]

Summary

TestMultipleTargets is randomly failing on the bots. The reason for that is that the
test is calling SBDebugger::CreateTarget from multiple threads.
TargetList::CreateTarget is curiously missing the guard that all of its
other member functions have, so all the threads in the test end up changing the
internal TargetList state at the same time and end up corrupting it.

[vsk]

Thanks, lgtm.

[JDevlieghere]

LGTM

lldb/source/Target/TargetList.cpp

 }
 
 Status TargetList::CreateTarget(Debugger &debugger,
                                 llvm::StringRef user_exe_path,
                                 llvm::StringRef triple_str,
                                 LoadDependentFiles load_dependent_files,
                                 const OptionGroupPlatform *platform_options,
                                 TargetSP &target_sp) {
+  std::lock_guard<std::recursive_mutex> guard(m_target_list_mutex);
   auto result = TargetList::CreateTargetInternal(
       debugger, user_exe_path, triple_str, load_dependent_files,
       platform_options, target_sp);
 
   if (target_sp && result.Success())
     AddTargetInternal(target_sp, /*do_select*/ true);
   return result;
 }
 
 Status TargetList::CreateTarget(Debugger &debugger,
                                 llvm::StringRef user_exe_path,
                                 const ArchSpec &specified_arch,
                                 LoadDependentFiles load_dependent_files,
                                 PlatformSP &platform_sp, TargetSP &target_sp) {
+  std::lock_guard<std::recursive_mutex> guard(m_target_list_mutex);
   auto result = TargetList::CreateTargetInternal(
       debugger, user_exe_path, specified_arch, load_dependent_files,
       platform_sp, target_sp);
 
   if (target_sp && result.Success())
     AddTargetInternal(target_sp, /*do_select*/ true);
   return result;
 }