[lldb] Add experimental target option controlling swift OS plugin

This is here mostly out of an abundance of caution, the default is to
use the plugins.

Author: felipepiovezan

lldb/include/lldb/Target/Target.h

@@ -199,6 +199,8 @@ class TargetProperties : public Properties {
 
   AutoBool GetSwiftPCMValidation() const;
 
+  bool GetSwiftUseTasksPlugin() const;
+
   Args GetSwiftPluginServerForPath() const;
 
   bool GetSwiftAutoImportFrameworks() const;

lldb/source/Target/Target.cpp

@@ -4496,6 +4496,17 @@ AutoBool TargetProperties::GetSwiftPCMValidation() const {
   return AutoBool::Auto;
 }
 
+bool TargetProperties::GetSwiftUseTasksPlugin() const {
+  const Property *exp_property =
+      m_collection_sp->GetPropertyAtIndex(ePropertyExperimental);
+  OptionValueProperties *exp_values =
+      exp_property->GetValue()->GetAsProperties();
+  if (exp_values)
+    return exp_values->GetPropertyAtIndexAs<bool>(ePropertySwiftUseTasksPlugin)
+        .value_or(true);
+  return true;
+}
+
 Args TargetProperties::GetSwiftPluginServerForPath() const {
   const uint32_t idx = ePropertySwiftPluginServerForPath;
 

lldb/source/Target/TargetProperties.td

@@ -31,6 +31,9 @@ let Definition = "target_experimental" in {
     DefaultEnumValue<"llvm::to_underlying(AutoBool::Auto)">,
     EnumValues<"OptionEnumValues(g_swift_pcm_validation_values)">,
     Desc<"Enable validation when loading Clang PCM files (-fvalidate-pch, -fmodules-check-relocated).">;
+  def SwiftUseTasksPlugin: Property<"swift-tasks-plugin-enabled", "Boolean">,
+    DefaultTrue,
+    Desc<"Enables the swift plugin converting tasks into threads">;
 }
 
 let Definition = "target" in {