LibThread: Hide Thread's constructor, as it is a Core::Object

Just constructing one of these guys on the stack willy nilly will leak
the first reference to them. There might be other C_OBJECTs that have
public constructors, seems like a good place for some static analysis
checks :).

Force users to call the construct() method for it.

Applications/Piano/main.cpp

@@ -74,7 +74,7 @@ int main(int argc, char** argv)
     Optional<String> save_path;
     bool need_to_write_wav = false;
 
-    LibThread::Thread audio_thread([&] {
+    auto audio_thread = LibThread::Thread::construct([&] {
         auto audio = Core::File::construct("/dev/audio");
         if (!audio->open(Core::IODevice::WriteOnly)) {
             dbgln("Can't open audio device: {}", audio->error_string());
@@ -102,7 +102,7 @@ int main(int argc, char** argv)
             }
         }
     });
-    audio_thread.start();
+    audio_thread->start();
 
     auto menubar = GUI::MenuBar::construct();
 

DevTools/HackStudio/HackStudioWidget.cpp

@@ -512,7 +512,7 @@ NonnullRefPtr<GUI::Action> HackStudioWidget::create_debug_action()
         }
 
         Debugger::the().set_executable_path(get_project_executable_path());
-        m_debugger_thread = adopt(*new LibThread::Thread(Debugger::start_static));
+        m_debugger_thread = LibThread::Thread::construct(Debugger::start_static);
         m_debugger_thread->start();
     });
 }

Libraries/LibThread/Thread.h

@@ -37,7 +37,6 @@ class Thread final : public Core::Object {
     C_OBJECT(Thread);
 
 public:
-    explicit Thread(Function<int()> action, StringView thread_name = nullptr);
     virtual ~Thread();
 
     void start();
@@ -46,6 +45,7 @@ public:
     pthread_t tid() const { return m_tid; }
 
 private:
+    explicit Thread(Function<int()> action, StringView thread_name = nullptr);
     Function<int()> m_action;
     pthread_t m_tid { 0 };
     String m_thread_name;

Services/AudioServer/Mixer.cpp

@@ -35,12 +35,12 @@ namespace AudioServer {
 
 Mixer::Mixer()
     : m_device(Core::File::construct("/dev/audio", this))
-    , m_sound_thread(
+    , m_sound_thread(LibThread::Thread::construct(
           [this] {
               mix();
               return 0;
           },
-          "AudioServer[mixer]")
+          "AudioServer[mixer]"))
 {
     if (!m_device->open(Core::IODevice::WriteOnly)) {
         dbgprintf("Can't open audio device: %s\n", m_device->error_string());
@@ -52,7 +52,7 @@ Mixer::Mixer()
 
     m_zero_filled_buffer = (u8*)malloc(4096);
     bzero(m_zero_filled_buffer, 4096);
-    m_sound_thread.start();
+    m_sound_thread->start();
 }
 
 Mixer::~Mixer()

Services/AudioServer/Mixer.h

@@ -132,7 +132,7 @@ private:
 
     RefPtr<Core::File> m_device;
 
-    LibThread::Thread m_sound_thread;
+    NonnullRefPtr<LibThread::Thread> m_sound_thread;
 
     bool m_muted { false };
     int m_main_volume { 100 };